Good afternoon, and welcome to Klaviyo's fourth quarter of fiscal 2023 earnings conference call. After the speaker's remarks, there will be a question and answer session. If you would like to ask a question during that time, simply press star followed by the number one on your telephone keypad. If you would like to withdraw your question, press star one again. We do want to incorporate as many analysts as possible on the call. Please limit to one question before returning to the queue. Thank you. With that, I'd like to turn the call over to Jack Grant, Senior Director of Investor Relations and Strategic Finance. Thanks, operator. I'm excited to welcome you to Klaviyo's fourth quarter and full- year 2023 earnings call. We will be discussing the results announced in a press release issued after the market closed today. Please refer to our investor relations website at investors.klaviyo.com for more information and a supplemental presentation related to today's earnings announcement. With me on the call today are Andrew Bialecki, Co-founder and Chief Executive Officer, and Amanda Whalen, Chief Financial Officer. During today's call, we'll make statements regarding our business that may be considered forward-looking under applicable securities laws and the safe harbor provisions of the Private Securities Litigation Reform Act of 1995, including statements concerning our outlook for the first quarter and full- year 2024. These forward-looking statements are subject to numerous risks and uncertainties that could cause actual results to differ materially from expectations and reflect our views only as of today. We assume no obligation to update any such forward-looking statements as a result of new information, future events, or changes in our expectations, except as required by law. For a discussion of material risks and uncertainties that could affect our actual results, please refer to the risks and uncertainties described under the heading "Risk Factors" in our quarterly report on Form 10-Q for the quarter ended September 30, 2023, filed with the Securities and Exchange Commission, or SEC, and in subsequent filings made by us with the SEC, including our annual report on Form 10-K for the year ended December 31, 2023, to be filed with the SEC, which may be obtained on the SEC's website at www.sec.gov and on our investor relations website. In addition, today's call includes non-GAAP financial measures. These measures should be considered as a supplement to, and not a substitute for, GAAP financial measures. Reconciliations to the most directly comparable GAAP measures can be found in today's earnings press release or earnings release supplemental materials distributed after market close today, which are available on our investor relations website. With that, I'll now turn it over to Andrew. Thanks, Jack. Thank you to everyone for joining us today. We are excited to share our fourth quarter and full fiscal year results, as well as updates across the business. The fourth quarter is critical to our customers, and we delivered for them. I want to thank both our partners and the Klaviyo team for ensuring our customers had a great holiday season. On today's call, we'll go through some of the highlights from the quarter, followed by some updates on products, our market, and I'll wrap up with our fiscal year 2024 focus areas. I'll then turn it over to Amanda to cover our financial results in more detail and provide our outlook for the first quarter and full- year 2024, before we open up the call for Q&A. We measure our success by our customer success. We helped our customers generate well over $50 billion in Klaviyo Attributed Value, or KAV, in 2023. Whether a business is just getting started or is already a household name like Mattel, we help empower smarter digital relationships and drive revenue growth. This was another strong year for our business as we grew our revenue 48% year-over-year and drove over $100 million in Free Cash Flow. The fourth quarter marked the first quarter that we generated over $200 million in quarterly revenue. We're continuing to see our strategy resonate across key growth initiatives. We're adding more customers, expanding with those customers, growing internationally, and scaling into the mid-market. Amanda will cover our progress on these growth areas in more detail. I'd like to call out a few notable moments from the past quarter. We know the holidays are very important for our customers, and we help power their growth. At the peak hour, our customers generated nearly $60 million in KAV. One of my favorite stories from the Black Friday, Cyber Monday, or BFCM weekend, was Jones Road Beauty. Jones Road is a nine-figure cosmetic company started by Bobbi Brown. The Jones Road team used Klaviyo to help drive a record-setting BFCM for their brand, with their KAV during BFCM up by over 150% year-over-year. Jones Road used many of the best practices we see working more broadly across the industry. They leaned into their loyal customer base with more personalization, driven by their segmentation strategy to execute this. We continue to provide our customers with an efficient channel to drive revenue that complements and amplifies their marketing spend on advertising networks. We're proud of stories like these, where we're able to drive growth for our customers and empower them to own their destiny. Collectively, our customers did a lot of marketing, and we were there for them to meet their demands. Our systems delivered 11.6 million messages per minute... and 14.7 billion total messages during the BFCM weekend. We delivered almost 2 times the number of total messages this Black Friday, Cyber Monday, compared to 2021. We're continuing to improve our product to ensure we are providing excellent deliverability for our customers. One of the recent focuses of our R&D team has been adding to our own lower-level email infrastructure to give us more control and visibility on how we deliver our customers' messages and reduce costs. We delivered over 1 billion messages through Klaviyo's mail transfer agent during the BFCM weekend. We're ensuring our platform can scale efficiently while providing customers with the tools they need to focus on driving revenue. We're continuing to turn the success we are powering for our customers into growing our own business. We're proud of the fact that some of the fastest-growing brands out there, including 8 of Numerator's top 10 fastest-growing CPG brands in 2023, and 7 of Retail Dive's top 8 DTC brands to keep an eye on in 2024, rely on Klaviyo to power their growth. 2023 was a banner year of brands choosing Klaviyo or expanding their business with us. Leading companies like Stanley 1913, Dollar Shave Club, Khloé Kardashian's Good American, Sugarfina, and Hum Nutrition all chose to drive their revenue growth with us. Our ability to easily harness our customers' first-party data continues to be a differentiator in the mid-market. We're excited that Fresh Clean Threads, a mid-market apparel retailer and one of the fastest-growing women-owned businesses in the country, chose Klaviyo during the quarter. Our 350+ native integrations and APIs are allowing Fresh Clean Threads to better leverage all of their first-party data for a complete view of their customers and drive more revenue. We're excited about our opportunity to continue to serve large customers. And more and more customers are looking to consolidate their tech stack and looking to us as the one vendor for their digital relationships. During the quarter, we saw European Wax Center consolidate their SMS channel with their existing Klaviyo email subscription. They are now able to create unified customer journeys across email and SMS, from marketing and customer outreach to appointment reminders and updates. Finally, we are continuing to see success expanding beyond our core retail and e-commerce markets. During the quarter, we added F45 Training, a fitness and training center operator with more than 1,800 locations, as a customer. With their previous provider, they were unable to build automations and flows into their customer journey. They're now going to use our Mindbody integration to help incorporate more automation into their marketing efforts to drive increased targeting and personalization. It's early days in these new vertical offerings, but we are seeing an increasing number of proof points in our ability to scale beyond retail and e-commerce. Now, I'd like to talk about a few things on the product front, particularly around artificial intelligence and our vision there. AI has changed the world and the way e-commerce marketers work. First, predictive AI made it easier to send the right message at the right time. Then, generative AI sped up the content creation process and made marketers more productive. At Klaviyo, we think the future of business-to-consumer marketing is autonomous. It's not just about AI that makes messages more personal and saves you time. It's about empowering you to generate and refine revenue-driving ideas effortlessly. Imagine a platform that not only creates tailored experiences for each individual consumer, but continuously learns and adapts, refining strategies for the best outcome in a fraction of the time. The brands who will win won't just be using one type of artificial intelligence. They'll be using predictive, generative, and autonomous AI to save time executing today's vision and building tomorrow's strategy. That's why today we're introducing Klaviyo AI, which empowers businesses to unlock revenue-driving opportunities and deliver exceptional consumer experiences across channels. AI has always been fundamental to powering Klaviyo, and today it's getting better with features like Segments AI, which generates complex segments for you in seconds based on simple audience prompts. And Forms AI, which uses artificial intelligence to optimize web forms for conversion by testing multiple versions of your form to find the highest converting display time automatically. And finally, you've been able to generate high-performing subject lines with AI, and now you can do the same for entire blocks of email content. Email AI is all about helping you work more efficiently. Simply type your campaign's goals, and Klaviyo will design an on-brand email section in seconds. Our customers have already seen the value of our artificial intelligence tools. Proozy, which offers a wide range of clothing options, including activewear, outerwear, and golf apparel from brands like Oakley, Adidas, and Reebok, started using our subject line and SMS AI to save time in early 2023. They called it a game changer. In addition to saving about 45 minutes a day in subject line creation, engagement improved too. Their SMS unsubscribe rate dropped by over 20% year-over-year.... We're excited to continue to build on this as we enter this new phase of marketing. In addition to our new offerings, the early feedback on CDP has been promising. One of our early adopters, Aura Frame, was able to drive efficiencies across their data management and reporting, specifically exporting CSV files, manually editing and cleaning data, and analyzing that data. As a result of adopting our CDP, they saved over 10 hours per week, consolidating their customer data under one roof, and supercharged their retention strategy for their 8 million app users. We shipped hundreds of new features for our customers in 2023. Just this past quarter, a new feature our customers were particularly excited about was our updated UI for our core flows functionality. This updated UI allows for improved editing, updated components, and a more modernized approach for our users. We're going to pair new launches with improvements to our core to provide the tools needed for our customers to drive revenue through an evolving landscape. One of the recent changes to our industry was around updated requirements from Google and Yahoo for large email centers. These focus on deliverability, spam, and the overall consumer experience. As a business focused on enabling our customers to drive more personalized and relevant consumer experiences, we believe these changes are positive for the industry. We care deeply about our efforts to ensure excellent deliverability for our customers, and many of the requirements are in line with best practices of how our customers were already using Klaviyo. We have been working with our customers to make it easy to ensure they are compliant with the updated requirements. For example, one of the requirements is one-click unsubscribe, which we built into our product in January, so it is a frictionless experience for our customers. We also launched a deliverability score for our customers to provide a clear view on their deliverability health. The updated requirements from Google and Yahoo went into effect in February and are continuing to roll out through April. To date, we have not seen material changes in consumer behavior as a result of these new requirements or seen anything that would indicate that they are materially impacting subscription sizes. At this time, we don't anticipate a meaningful impact to our business. Over the long term, we believe that the companies that provide their customers with the ability to deliver personalized, targeted, and relevant content will win the market. We have a few key priorities to continue to drive strong growth this year. We're continuing to invest behind our four near-term growth drivers, adding more customers, expanding with those customers, expanding internationally, and growing into the mid-market and beyond, while planting seeds for longer-term growth. Within R&D, we are building more tools for customers of all sizes across the globe to make it even easier to use Klaviyo. We'll be launching new features focused on the mid-market and continuing our internationalization and localization efforts. While doing this, we're going to keep building more artificial intelligence into our platform to make it even easier for our customers to build smarter digital relationships. On the go-to-market front, we have a few focus areas. Within sales, we are growing our sales capacity across our teams, focused on mid-market and international new customer acquisition and cross-selling into our install base. For our larger customers, we are focused on supporting these customers with cross-functional teams to drive further adoption and expansion. Klaviyo is the marketing platform that powers smarter digital relationships. Marketing is focused on evolving our brand and narrative to better tell the story of our whole platform capabilities for businesses. Finally, we're going to continue to invest behind growing our 5,000-plus partner ecosystem to ensure our customers have the right agencies, system integrators, and technology partners to help them succeed with Klaviyo. A great example of this is our recently announced partnership with L Catterton to enhance the marketing capabilities of their portfolio company. We'll be further building out our ecosystem this upcoming year and beyond. And with that, I'll turn it over to Amanda to cover the financials in more detail. Amanda? Thanks, Andrew. Today, I will provide a brief overview of our fourth quarter and full- year 2023 financial results and discuss guidance for our first quarter and full- year 2024. As a quick reminder, today's discussion includes non-GAAP financial measures. Please refer to the tables on our earnings release for a reconciliation of GAAP to the most directly comparable non-GAAP financial measures. We are pleased with our financial performance. We continue to see rapid growth at scale in an efficient manner, in line with our financial framework. In the fourth quarter, we generated $201.6 million in revenue, representing year-over-year growth of 39%, and we delivered an 8% non-GAAP operating margin. The fourth quarter is seasonally strong for us due to the holiday shopping season and how our business model scales with our customers' growth. We delivered for our customers during their most critical time of the year and shared in their success. Our growth is powered by four main vectors: adding new customers, expanding with those customers, expanding internationally, and growing into the mid-market. We continue to perform on each of these vectors. In terms of adding new customers, we increased our customer base 20% year-over-year and are proud to now serve over 143,000 customers. We are continuing to expand with our customers, as evidenced by our dollar-based net retention rate, or NRR, of 117%. 16% of our customers now use our SMS offering, up two percentage points from last year, which highlights the value customers see in our platform capabilities. Internationally, our aggregate revenue from EMEA and APAC increased 46% year-over-year in Q4 as we continued to increase our global footprint. Finally, we're seeing more and more businesses in the mid-market turning to us. We ended the fourth quarter with 1,958 customers, generating over $50,000 in ARR. This represented 80% year-on-year growth, and Q4 was the largest quarter in company history for net customer adds of this cohort. Success with our larger customers is evident in our annualized revenue per customer as well, which was $5,600 in Q4, an increase of 16% year-over-year. As expected, our NRR saw a slight decline from the prior period due to the impact of lapping our September 2022 price increase. Historically, our customers dial back their SMS spend after the holidays, which we experienced at the end of this year. In the last two weeks of December, we saw customers being more thoughtful compared to prior years with regards to the level of their overall spend, particularly among customers who use our SMS offering. Looking ahead, we expect these trends and the price increase lapping to pose headwinds to NRR in the coming quarters. Our customers continue to drive strong KAV through our platform's capabilities, particularly through the ability to personalize and segment their consumer bases. This high ROI helps drive strong customer retention. Moving down the income statement, I will be discussing results on a non-GAAP basis. Gross profit for the quarter was $159.8 million, representing a gross margin of 79%. This marks a 5-point improvement compared to Q4 2022. During the quarter, we incurred a $4 million benefit or 2 of the 5-point improvement from milestone-based credits related to our cloud hosting. We continue to see the benefits of our R&D team's efforts on system and cloud engineering optimization. Our efforts around KMTA that Andrew highlighted are a great example of this. Through these initiatives, we are able to provide better customer experiences while simultaneously increasing our efficiency. Looking ahead, while we expect to see these help to offset a part of the higher cost associated with the SMS channel, we do expect a couple of points of headwind on our gross margin this year. Turning to operating expenses, sales and marketing expense was $77.3 million, or 38% of revenue for the quarter. As we said last quarter, areas we are investing in include marketing program spend and sales headcount to grow our capacity. We continue to closely monitor the unit economics of different investments we are making, and we will continue to make investments where we see the right level of returns. Some of our investments in the mid-market take a bit longer to yield than SMB investments, but drive strong overall ROI. R&D expense was $37.8 million or 19% of revenue. We're continuing to invest behind our product, AI capabilities, and our newer offerings. Finally, G&A expense was $28.5 million, or 14% of revenue. This is an area where we expect to continue to get more leverage over time. For Q4, our operating income was $16.2 million, representing an operating margin of 8%. For the full- year, we finished with an operating margin of 11%, marking a 17-point improvement compared to fiscal 2022. We also generated free cash flow of $34.7 million during the quarter and $110 million for the year. Our full-year free cash flow margin was 16%, an improvement of 25 points year-over-year. Our performance this year further supports our belief that we do not need to choose between growth and generating cash flow as we invest to drive long-term growth. Finally, turning to the balance sheet. We finished the quarter with $739.7 million in cash, cash equivalents, and restricted cash, with no debt. One note for your models is that during the quarter, we did net settle vested equity using $18.8 million of cash, which is reflected in our financing activities, and this activity is excluded from free cash flow. Now I'd like to talk about our outlook for the first quarter and full- year 2024. As a reminder, we experienced typical seasonality in the business. As I mentioned earlier, Q4 is our strongest quarter as a result of Black Friday, Cyber Monday, and the holidays. In turn, Q1 is our seasonally lightest quarter as customers traditionally pare back their spend in response to consumers tightening their belts after the holidays. Q2 and Q3 typically exhibit modest sequential upticks before picking back up again in Q4. Looking ahead, we assume the linearity of revenue by quarter in fiscal 2024 will follow the trends we experienced in 2023. Given the current macro environment, we're setting our guidance with prudence and factoring a continuation of the recent trends we've seen in customer spend into our guidance. For the first quarter, we expect revenue to be in the range of $201 million-$203 million, representing growth of 29%-30% year-over-year. We expect non-GAAP operating income to be in the range of $22.5 million-$25.5 million, representing a non-GAAP operating margin of 11%-13%. In the first quarter, we are continuing to invest, particularly in our sales capacity. In addition, we expect Q1 free cash flow will be muted due to the timing of vendor payments. For the first quarter, we expect fully diluted shares outstanding to be 297 million. For the full- year, we are guiding revenue to be in the range of $889 million-$897 million, representing growth of 27%-28% year-over-year. We expect non-GAAP operating income to be in the range of $94 million-$102 million, representing a non-GAAP operating margin of approximately 11%. As we highlighted last quarter, in fiscal 2024, we are making investments across go-to-market and product to set Klaviyo up for long-term growth. Based on the timing of these investments, we expect to see some deleverage year-over-year in operating margin in the first half of the year as we front load investments. We expect more leverage in the latter part of the year as we head into our seasonally strong fourth quarter. Finally, for the full- year, we expect fully diluted share count to be 299 million. To close out, we delivered strong results this quarter, with rapid growth on the top line and a healthy bottom line with strong free cash flow generation. We are excited for this year and for the long-term opportunity ahead of us, and we are focused on executing against it for our shareholders. With that, we'll open up the call for Q&A. Operator? If you would like to ask a question, simply press star followed by the number one on your telephone keypad. As a reminder, please limit to one question before returning to the queue. Your first question comes from the line of Remo Lenschow with Barclays. Your line is open. Hey, congrats from me. Two quick questions. One, it'd be like, there's a big discussion in the industry going on at the moment about like, you know, how some of the internet providers want to limit spam. Can you talk a little bit about what you're seeing, how that's impacting your customer conversations, what customers are doing there? And then I had one follow-up from Amanda, please. Yeah, great. Thanks, Remo. So first on some of the changes from you know, Google and Yahoo and others, you know, as we talked about in the prepared remarks, at this point, we haven't seen and we're not anticipating a meaningful impact to our business. You know, we've been working with our customers to get them compliant with updated regulations, and well, actually, not all of our customers even qualify as bulk senders. They don't send enough email volume. We're actually working to get our entire customer base compliant, and a lot of that compliance is happening automatically through our product. We built it in directly, so actually, you know, our customers don't have to do they have to do very little work. So on the customer side, we're feeling really good about where they're at. On the consumer side, we're also watching that as well, and thus far, we haven't seen any changes in consumer behavior. To give you, like, a couple of data points, we measure unsubscribe rates from email, and we've seen that increase by only 0.007%, so a really small number. And then we also watch for things like spam rates, and, you know, while we don't have perfect visibility into that, when we talk to customers anecdotally, we're not hearing of any broad changes in the reports of spam reports. And, for some, you know, ISPs, we actually can get the data from them directly, and we're not observing, you know, material increase in spam reports there as well. So, overall, we feel really good about our customers, consumers. And then just more broadly, we think it's a great thing for businesses in reducing, you know, the amount of spam and noise that consumers get in their inbox. I think, you know, product and platforms like ours that focus on delivering the right content, highly personalized, and that's what consumers find the most engaging, and that's what inbox providers love. And so we think as long as we stay true to doing that, you know, the businesses that we serve will be in great shape. Perfect. Thank you. Yeah, that's very clear. And then, Amanda, if you think about the investments in the first half, can you, since, you know, you're a relatively new company on, on the, in the public market, can you talk a little bit about the, the time between investments and returns, like in terms of how long does it take to, like, for example, see those guys to get productive, et cetera, just to help us understand like the dynamic between investment and, and returns? Thank you, and congrats from me again. Thanks, Remo. Yeah, you know, as we think about the timing between investments and returns, we are always focused as we talk about the unit economics that we get when we make these investments. So as we think about it, we've always been, going back to Andrew and Ed, bootstrapping the business in the original days, focused on investments that make a fast payback in terms of the CAC payback. So you know, that's one of the beautiful things about a model focused on SMBs, is that they tend to have shorter payback periods associated with them. In the mid-market, as we're making investments there, we do see a bit longer payback. Just the nature of those investments is that they are larger upfront. They take a little bit longer to pay back, but that they have really strong LTV to CAC. So as we're making these investments, we're watching that, and then we're managing across the portfolio to make sure that the balance across those two is healthy for the business. And it's important also to remember, in our business, whether it is in the SMB section or in the mid-market portion of the business, that our sales cycles are pretty short relative to others. You know, we measure our sales cycles in weeks, not in months, and so these investments tend to have a pretty nice payback period as they ramp up. Thank you. Your next question comes from the line of Elizabeth Porter with Morgan Stanley. Your line is open. Excellent. This is actually Keith Weiss sitting in for Elizabeth. Congratulations on a really nice quarter. Two questions. One on the 50K customer adds, really impressive number of 80% year-on-year. Can you talk to us about what's driving that growth? And to the extent of like, how much of that is coming from existing customers just growing to be a 50K customer, taking on SMS, maybe taking on CDP, and just expanding their size, versus how much is like a net new mid-market customer motion of customers coming on in that mid-market realm of that 50K+ realm? And then I have a follow-up for Amanda as well. Awesome. Thanks, thanks, Keith. So to comment, yeah, I mean, we're also very excited about the progress we're making in mid-market. You know, that, that 80% year-on-year growth for 50K customers, is a great number. And I think it's, emblematic or it's, demonstrates the shift that we're seeing, with mid-market enterprise brands as it relates to their marketing. They're looking for one customer platform, one database for- to be that source of truth for their customer record, and they're looking to layer marketing and then additionally, other applications on top of them. So just to give you an example, there's a large cosmetics company that we work with that initially used Klaviyo for our marketing products, email and SMS, but in fact realized, you know, recognized that, gosh, Klaviyo is this central database for all of their consumer data, and now they're using our API to integrate that into other parts of the customer experience, for instance, the website, their mobile app, as well as customer service. So that's what we're seeing play out there. As it relates to, like, the mix, it's actually, it's a healthy, it's a healthy part of existing customers expanding, you know, initially with SMS, but now increasingly with CDP and reviews as well, as well as just net new lands. We've had some of our largest new logo lands, even in the last few months. So there's a lot more to do there. I mean, we're constantly working on feature development, scalability of our platform, but we think we've got really good product market fit. And this story around consolidation, or really the different parts of your consumer tech stack integrating together, that's a really, really durable trend. Got it. That makes a ton of sense. And then, Amanda, on the gross margin side of the equation, huge outperformance versus kind of where you guided to. I appreciate the clarity on the, like, a $4 million benefit from milestone credits. When we're thinking about the couple points of pressure in gross margins from this year, I just wanna make sure we're basing to the right number. So should we start at the 79% level, or are those, like, milestone credits, that was, like, a point in time, so it's like we should start at 77% and then see a couple points of pressure from there? Like, can you just help me anchor, like, what's the right number that we should be starting from, where we're gonna see those couple of points of pressure? Yeah. So I would think about the first half of the year, gross margins being in the high seventies range. And I think you're thinking about it right, which is that over the course of the year, you're gonna see two factors happening in our business that will somewhat counterbalance each other. On the positive side, we have the great benefits that we continue to see from the cloud engineering optimization that our R&D team has done, combined with some pricing negotiations that we've had on our supplier side, and those are helping to support and to drive higher gross margins. The counterbalance to it is, as our SMS business grows and expands, that creates some pressure on gross margins. So the balance of those over the course of the year, we think, will continue to have support from the engineering optimization, but it'll be offset by the SMS expansion. Got it. That's super helpful. Thank you so much, guys. Your next question comes from the line of Gabriela Borges with Goldman Sachs. Your line is open. Good afternoon. Thank you. AB and Amanda, I wanted to follow up on Amanda's comments on customers being more thoughtful versus prior years with their level of spending. Maybe a little more color on what you're seeing in the health of the installed base and what you think is driving what sounds like a little more muted outlook on the macro beyond just the typical one Q seasonality? Sure. Thanks. Thanks, Gabriela. Great, great question. So what we saw in Q4 with customers being more thoughtful was particularly true for customers who use our SMS product, in addition to those who are using the email. And if you think about it, SMS costs more per message than email. So as customers mature in their usage of SMS, we're seeing a couple of things happen. First thing that we're seeing is that they're being more thoughtful and more targeted with the messages they send to make sure that they're driving high ROI from those messages. And then the second thing is that they're learning how to be more proactive in managing their subscriptions and managing their plans to make sure that the subscription size aligns with the size of their usage in any given month. Now, if you remember, one of our operating principles as a business is that we align our business with the value that we provide for our customers. So we think that that high ROI and the fact that we're able to help customers send really targeted messages that generate that high ROI, creates stickiness in the platform, and that stickiness shows up in really strong retention. The other thing that that stickiness and that high ROI does, is it helps us earn the right over time to share in that value that we create for customers. Now, as you think about this and how, you know, it relates to our guidance for the year, we've spoken before about the fact that as a company, we're a company who strives to provide a realistic view on our, on our business. We're prudent in the way that we forecast, so that we're confident in our ability to deliver. It's also important to keep in mind, we're a scale business. We have over 143,000 customers. We have a decade plus of operating history, and all of that data gives us a really strong foundation for forecasting. It is not our intention to be a company who's going to significantly overexceed the outlook that we provide. What we're really trying to do is share with you and with our investors, a clear view of the health and the trends that we're seeing in our business. Thank you for the color. Your next question comes from the line of Brent Bracelin with Piper Sandler. Your line is open. Thank you. Maybe I'll start with you, Amanda, here. If I think about the growth algorithm, 20% customer growth, ARPC growth, now that we've anniversaried the price increase was 16%. That was actually similar to what you saw prior to the price increase. Can you just talk about what is driving ARPC growth and how sustainable that is? Thanks. Yeah, you know, I think you're thinking about the right things, which is, that as our business grows, you know, we have that install base that's continuing to grow and that we're continuing to sell more products to them. So overall, as we think about the business going forward, we think about continued strong growth, powered by new logos in combination with the expansion with those customers. In new logos, increasingly, we are moving upmarket. And as we move into the mid-market, you'll continue to see strong logo growth, but maybe with more of the mix driven by higher ASPs, as opposed to being driven by, you know, higher logo counts going forward. You know, if you think about other drivers of expansion and what that expansion with our business looks like over time, as I just mentioned, our gross retention remains consistent. It remains healthy. We see customers sticking with the platform over time. Then we continue to see customers grow their subscriptions as they add new products. So net-net, you know, I think what we'll see going forward is this balance, and a healthy balance between new logo acquisition as well as that upsell and cross-sell that drives that strength and revenue per customer. Helpful color there. And then, AB, you mentioned that the email infrastructure investment, I think it was 7% of your Black Friday, Cyber Monday volumes were sent through that new infrastructure. Can you just double-click into the benefits? Why are you doing that, and then how quickly should we see volumes ramp into that infrastructure? Thanks. Sure. Yeah, that Klaviyo MTA, so kind of the underlying email infrastructure, really some excellent engineering by our R&D team. So the purpose of that is, if you think about Klaviyo, we've done a lot to verticalize the stack, integrate the different pieces, from how you store customer data, to how you design messages, and then obviously, just extend that into how you deliver, in this case, email messages. So one of the big benefits to us is we've talked a little about deliverability. Owning that infrastructure, there are some, you know, cost advantages, but actually, the real thing for our customers, it gives us much more visibility into how their messages are performing. So both gives us more control on deliverability, but also visibility that we can then pass to our customers so they can go get better results. So that's an example of where, you know, I think we're, we're gonna be aggressive on engineering our own solution to problems where we think we can do a job of basically vertically integrating different parts of the customer experience. So very excited about that. And then, you know, on the part of volume ramping, we're being, you know, judicious about how quickly we ramp up volume. But the fact that we sent over 1 billion messages over the Black Friday, I mean, it's just a testament to the quality of the engineering that we've done. Helpful color. Thank you. Your next question comes from the line of Arjun Bhatia with William Blair. Your line is open. Perfect. Thank you, all, and my congrats on the quarter. Andrew, maybe I want to touch a little bit on the other side of some of the changes at Gmail and Yahoo! And, you know, maybe, you know, we'll combine that with cookies getting deprecated this year. Can you just talk a little bit about what that means for personalized messaging, email, text, et cetera, and what your kind of data segmentation and personalization capabilities, what kind of benefit, if, if any, that might accrue this year from a, a greater emphasis on first-party data over third-party data? Absolutely. Well, so I think, you know, at Klaviyo's core, our whole ethos is around giving businesses ownership of their consumer data. So, you know, we actually help businesses collect or use, you know, cookies, first-party cookies, and the emphasis on that to collect more of that data. So in this case, you can think about browsing behaviors like what products that somebody's looking at, adding to their cart, and then using that to build it back into some of the personalization algorithms that we have. So I think this is a, it's a net good change for the industry. It's also for privacy, also a net good change for our businesses. You know, we talked a little about, like in the mid-market, the same is true for SMBs. The most important data asset that any consumer business is building is their customers. So we look at our job as to, one, help them pull all that together, and so we've built a bunch of tooling to help with the, the sunsetting of some of the third-party cookie technology. But then also critically, like, how do you tie that, you know, central source of truth back to action? So embedding it into marketing, and I gave the example of, some of our more sophisticated customers starting to use that data directly on the website. That's something actually we're very excited about, starting to productize, you know, over the next, you know, coming months and coming years. ... Okay, super helpful. And then if I can touch on the AI capabilities that you're launching, those seem—or the generative and autonomous AI capabilities, all these seem incremental and new. How are you thinking about kind of capturing some of that value, additional value that you'll deliver to customers over time through pricing for those capabilities? Yeah, great. So I'm, you know, very excited today with our launch around Klaviyo AI. It's one of those launches I've been most excited about over the last couple of years. You know, we've been investing in AI for the last four, five, six years, and we've been iteratively building that into our core technology. And you can think about when we talk about the future of marketing, really the future of, like, customer experience at CRM is autonomous. That means that we're thinking about using AI not just for productivity gains, but literally to drive better performance. And that means more revenue for our customers, and being able to do that autonomously, freeing up marketers to get back to the, like, the core of marketing. Coming up with ideas, thinking through strategy, and then being creative, working on the brand. So Klaviyo AI for us is, you think about the things that existing AI features, bringing those into one toolkit, and then adding a couple of really cool pieces. So a lot of you talk a lot about generative AI with segmentation, querying, finding interesting sets of customers. We've made that a lot easier by now allowing users to define those queries with natural language and return in seconds. We also talked about the creative side with Email AI, being able to design whole chunks, whole pieces of an email just from a natural language prompt. You combine that, those generative capabilities, with also, like, some of the automatic optimization. We talked about Forms AI, and the ability that you can create a form on your website, and we'll actually tune a lot of the variables for you to optimize its performance. So you add all that stuff up, and what it means for our customers is literally better results. To give you an example, one of our customers, WillowTree, you know, in the summer of last year, they started using more of our predictive analytics and some of our segmentation capabilities. They were able to do that, to use machine learning and AI, to find sets of customers that were hard to discover. They started sending email campaigns to those customers, and it literally grew their revenue from email by over 50% in the back half of last year. That's an example of the kinds of lifts and opportunities that are out there when you apply artificial intelligence to the domain of marketing. And then, you know, when you think about monetization, you know, we're not directly monetizing this today as a separate SKU. I will note that, like, our Forms AI capabilities do increase the number of profiles into Klaviyo, which we do monetize through our email product. But we're not really directly monetizing our AI toolkit as one. Now, over time, we do think there's a real opportunity that as we add more of these capabilities, we make marketing increasingly more autonomous, put marketers in that, you know, kind of director's chair. There will be an opportunity to monetize on the dollar uplift that we provide. Your next question comes from the line of Tyler Radke with Citi. Your line is open. Yeah, thanks for taking the question. Amanda, going back to the commentary around what you saw at the end of December, can you just talk about, did that have an impact on total customer additions as well? I think total customer additions in Q4 was a little bit below what you've typically seen in Q4. And then just curious, has that softness in the SMS side continued into January or February, or do you think that that was just kind of an end-of-December event? Thank you. Yeah, thanks, Tyler. Great question. So, you know, I would take them separately and think about them as two separate things. On the net customer adds and what we're seeing there, you know, if you think about where is our sales and marketing engine pointed, our sales and marketing engine is largely pointed at SMBs in the mid-market. And so as we focus more of our sales and marketing efforts upmarket, we expect that we're gonna see larger customer lands, which you see in the 50K customer, and in the expansion in the average revenue per customer, with maybe not as much expansion at the lower end of the market. At the same time, you know, we are entrepreneurs at our roots. You know, we think that we are a great place for businesses of all sizes to drive growth. So the way that we think about continuing to drive those adds at the lower end of the market is really through product, and building a great product that makes it easy for everybody to use. But as you think about building the models, and as we think about our outlook going forward, we've factored these trends, which would be maybe more moderate customer adds and more growth in revenue per customer, into our algorithm and our financial outlook going forward. And then as for your question about what are we seeing in January and February, I would say the trends of January and February are similar to what we spoke about at the end of Q4. So, you know, given the macro environment, we just see customers being more thoughtful about their spend. They're making sure that their plan sizes aligns to their usage. They're making sure that their messages are highly targeted and that those messages are driving high ROI. We've built that into our guidance, and over the long term, we appreciate that because we want our customers to be sending really targeted, personalized, high ROI messages. Your next question comes from the line of Rob Oliver with Baird. Your line is open. ... Great. Thanks, guys. Good afternoon, and thanks for taking my questions. I'll, I'll squeeze in two as well, AB, one for you, and then Amanda, one for you. So AB, you, you called out the, the fitness win that came by via the Mindbody partnership. And obviously, mid-market, very strong for you guys. And just wanted to get a sense of of how we should expect that, you know, that, that progression away from, you know, internet retail when you, when you look within sort of the pipeline and talk to your sales and, and marketing folks, how we might expect that to play out, that diversification, throughout 2024. And then, Amanda, just for you, just the my follow-up is just, just around the, the NRR trends. You know, clearly, it seems like a big, you know, obviously, big difference between what we would see at SMB versus what we'd see mid-market and up. Just curious, you know, not expecting to break that out, but just wanted to get a sense from you of, you know, have those trends held steady? Have they been stronger than expected up at the high end of the market? Any color there would be really helpful. Thanks, guys. Great. Thanks, thanks for the question. So to speak a little bit our growth outside of, you know, e-commerce. So it's still early here, but I'll give you a little bit of color. We're seeing, you know, it's early, but we're seeing some really encouraging signs of more businesses, you know, outside of e-commerce and retail moving over to Klaviyo. So that cohort still represents less than 5% of our revenue, you know, due to the strong growth we're seeing in e-commerce, but it's growing really rapidly. So we talked about European Wax Center, F45 Training. I'll give you one more. You know, there's a pizza chain, a national pizza chain, with over 300 locations. You know, they also consolidated down marketing spend onto Klaviyo. They bought both our email and our SMS products, and they're taking advantage of our integration with Olo, as well as another point-of-sale system, to essentially manage all of their first-party consumer data. So that, that is gonna do the same thing we're doing with e-commerce. That's gonna allow them to create many more targeted campaigns, more automation, and ultimately drive more sales. So if you back up a little bit, like, for all of our customers, there is focus than ever on the importance of having direct relationships with their consumers in building their consumer database. We're seeing that in e-commerce, in retail, and beyond. And I think we're also seeing everybody focused on collecting that data as well as how to leverage that data and put it to work. I think we've got really good product-market fit, both within e-commerce and retail, and then we're seeing, you know, with new vertical expansion, that that product-market, product-market fit extends beyond that. Yep, and as regards to, NRR and how it varies depending on customer size, I would not really call out any strong variation depending on the size of the customer. But we do see in our mid-market customers that they tend to have more SMS. So some of the trends that I talked about as being more pronounced among SMS users maybe impacts the mid-market more, but it's really, I think, more of a question of the product that they're using and the way that they're being more thoughtful about how they use that higher price per message channel than it is necessarily related to, you know, what we've seen in the size of the business. You know, related to what we're doing about that and overall the way we think about the course of the year, we are really doubling down on how do we help our customers with best practices. So what are the things that we can do to help them generate the highest ROI that they can, and to continue to drive the usage so that they're getting, you know, great KAV growth coming out of these channels? 'Cause we think that that ability to generate high KAV per message is a real differentiator for us. Not only helps our expansion as we drive that, but it also helps strong retention as well. Really helpful detail all around. Thank you, guys, very much. Your next question comes from the line of DJ Hynes with Canaccord. Your line is open. Hey, guys. Thanks for taking the question. So maybe just building on Rob's last question there. AB, I totally understand the comments on spend thoughtfulness on SMS, given the higher cost to use. I wanna ask about KAV conversion versus, you know, for email-only customers versus those that are using email and SMS. Is there a discernible difference there? Which I guess gets at the question of, is SMS working the way that you hoped? Sure. So, one, I'm very excited about the amount of KAV we drove last year, over $50 billion, and that continues to be a North Star for us. And like I said, you know, our customers are—they're trying to consolidate their first-party customer data, and then it's how do you put that to work to deliver experiences that actually drive conversion? So to the question about like, difference between email and SMS, no, we're not seeing any material changes there. And, you know, as we've said before, you know, SMS has a slightly different cost structure, so the ROI there is always going to be a little bit different. However, we're seeing from both channels, customers really getting great results. One of our goals is, you know, focus on getting more personalization, more segmentation, both, you know, through our product, through the artificial intelligence we're layering into the product. We're helping them discover more and more use cases that they can apply to their customers to deliver better experiences, but also help monetize them better. Got it. Thank you. Your next question comes from the line of Terry Tillman with Truist Securities. Your line is open. Yeah, thank you, Andrew, Amanda, and Jack, for taking my question. I'm gonna pivot from SMS and just ask about international. Well, it is actually a multi-part, but it's a single question. Should we expect that that just drifts higher as a percentage of revenue? And is it still more in 2024 where you're getting pulled in to that market, as opposed to more of you're directly kind of attacking it with a lot of boots on the ground? And then, are you seeing some potential benefits from Shopify in that market? Because they're talking about some pretty substantial growth in EMEA. Thank you. ... Awesome. Thanks, Terry, for the question. So on international, yeah, I mean, obviously, that's another area that we're very bullish on. We continue to drive strong growth there. You know, our aggregate EMEA and APAC revenue was up over 40%. So, without commenting on the distribution, I think we're seeing strong growth domestically as well. I'll tell you that we're very excited about where international is going. It's one of our four key drivers. So on that front, you know, there's a couple of things that we're doing. On the product side, we still have an internationalized and localized Klaviyo core interface. That's something we're working on, and we'll ship later this year. And then on the go-to-market side, we're, you know, as Amanda talked about, we're very thoughtful about how we go to market. You know, because our history is as a product-led company, our strategy to grow internationally is also product-led. We're putting our product in market, watching to see where there's adoption, and then following those trends. And, with Shopify and others, you know, a big part of our international strategy is working with partners, both globally and locally. So I expect that we're going to see really nice growth there. And, yeah, we're excited about what we're seeing. Thank you. Your next question comes from the line of Siti Panigrahi with Mizuho. Your line is open. Thanks for taking my question. I wanted to ask about CDP that you guys, you know, announced a few months back. Wondering what kind of feedback you have got so far, what kind of interest or use cases you're seeing there? Yeah, great. So, our CDP product launched last summer. And you can think about CDP, and especially the reporting and analysis use cases, we're seeing a lot of customers adopt those. So to just give you an example of how our customers are using CDP, there's a large pet retailer that's taking advantage of some of the advanced analytics you can do around frequency and recency and spend. So finding customers who used to be really loyal but have since lapsed. And they're using that, doing that analysis inside of Klaviyo on the Klaviyo core database, and then immediately able to turn that into email and SMS automations and campaigns and monetizing those. So that's the kind of... What we're seeing is a lot of that kind of behavior. It's we're tightening the loop between traditionally what was analytics in one part of the company, one set of tools for that, and then actually activation, putting it to work in a different part. Those two worlds are merging. So it's still early there for us, but we're excited about what we're seeing with CDP, and I think there's a lot more, you know, adoption that's coming this year. Thanks, AB. Your next question comes from line of Scott Berg with Needham. Your line is open. Hi, everyone. Nice quarter for me. Amanda, you had a pretty impressive year last year in terms of free cash flow margins from the year-over-year improvement there. There's about a 5-point spread in between operating margins and free cash flow margins for the year. Is that the right way to think about fiscal 2024 as well, or will there be some divergence there, even after taking into account some of the spending in the first half? Thank you. Yeah, great question, you know, and thank you. I appreciate you calling it out. It's 17 points of operating margin expansion year-over-year. It was indeed a very strong year. In general, over the long term, I would expect that because the majority of our customers are month-to-month, and those payments are coming in monthly, that our operating income margins and our Free Cash Flow margins are going to track relatively closely over time. You may see some variation year-to-year, just literally depending on the timing of when some payments happen to particular vendors. But in general, you should see those tend to track pretty closely to each other. Excellent. Thank you. We have time for one more question, and that question comes from the line of Derrick Wood with TD Cowen. Your line is open. Great. Thanks. Amanda, there was a big sequential increase in sales and marketing expenses in the quarter. Are you able to dimensionalize how much of this was seasonal marketing spend versus how much of it was adding headcount? And I guess, as a follow-up to AB, just would love to hear kinda how sales hiring activity has been trending over the last few months, and how you're feeling about ramping reps to productivity and kinda creating some new growth levers upmarket with new capacity as you progress in 2024. Yeah, great. I'll start and then I'll let Amanda add on. So, we're very excited about the sales and marketing investments we're making. We mentioned that some of the key growth levers of not just growing number of new logos, but getting customers to expand with us, the number of products they buy, expanding into the mid-market, expanding internationally. So there's really two drivers of our sales and marketing investments to date. The first is, as you mentioned, is increasing sales capacity. And we're focused in a couple of areas: international, mid-market, as well as expanding what we call our customer growth team, which is about driving more of our customers to adopt a greater portion of the Klaviyo product set. So that's part number one. And the second part is, we're making additional investments into marketing. We have a lot of customers who are, like, super fans of Klaviyo. We're using their stories, these customer testimonials, as, you know, a lead-in to find additional customers. So we're ramping up that marketing investment and sharing those stories of success to drive awareness, top of the funnel, and ultimately, you know, net new customer acquisition. So in general, like, while those are the two drivers, like, Amanda and I, we're still very strong believers in the roots of what Klaviyo was founded on, which is good unit economics. So we're going to continue to experiment, but also be very disciplined, and closely monitor the economics and the ROI of those investments. Yeah, and if you think about, you know, how to build your models and how the investments might flow over the course of the year, more of the investments, as we mentioned on the call, are weighted towards the first half of the year, as we're investing to build that sales capacity to ramp up heading into the back half of the year. And then historically, seasonally, we have ramped up marketing in the third quarter, as we prepare for heading into Black Friday, Cyber Monday, and so I would expect those trends to continue. Great. Thank you. Those are all the questions I have for today's call. With that, I'll turn the call back over to Andrew Bialecki for closing remarks. Great. Well, thank you all for joining us on today's call. I want to thank again the entire Klaviyo team for their great work delivering for our customers in 2023. As we say internally, we're 1% done, and we're excited for the year ahead. We'll be attending the KeyBanc and Morgan Stanley conferences in March and look forward to seeing many of you there. Have a nice evening. This concludes today's call. You may now disconnect.