Thanks, Chris. And thank you everyone for joining us today. Before I begin, I'd like to remind everyone that we have posted supplemental financial slides to our Investor Relations website to accompany today's presentation. As Tim mentioned, we are pleased to report that once again we exceeded our previously issued guidance for revenue and EBITDA in Q4. That represents the fourth consecutive quarter that we have exceeded our expectations since we went public in February of last year. We are also seeing an acceleration in spending across our platform going into Q1 2022, which we expect will continue throughout the year, which is a testament to the increasing customer adoption of our platform. This afternoon, I will be discussing some of the highlights of our Q4 and full year 2021 performance, as well as our current expectations for 2022 and our longer term expectations for the business. With that, let me discuss some key financial and operational highlights for the quarter and the full year 2021. In 2021, Viant's business continued to scale and performance accelerated, yielding new record results and we finished the year on very strong financial footing. We continue to see the benefits of our recent WWC software release. With customer adoption increasing across all channels where cookies or device identifiers do not exist or are limited, such as connected TV, mobile, streaming audio and digital out of home. Further investment in our team and technology has also paid dividends, as evidenced by the significant increase in the number of active customers and the average contribution ex TAC per active customer over the last year. We also benefited from the cohort effect of customers ramping spend, the longer they are on the platform, and that trend is expected to continue. In terms of top line metrics, for the fourth quarter total advertisers spend across our platform increased 26%. Revenue for the quarter was $82.7 million, an increase of 46% over the prior year period. And contribution ex TAC for the quarter was $48.5 million, an increase of 24% over the prior year. For the full year 2021, total advertisers spend across our platform increased 29%. Revenue for the year was $224.1 million, an increase of 36% over the prior year. And contribution ex TAC for the year was $141.5 million, an increase of 28%. Our recent WWC software release continues to drive an increase in omni-channel adoption by our customers, as they can now leverage our unique Household ID to seamlessly buy and measure their ad spend across all digital channels. Currently, half of all advertisers are using WWC and our Household ID for targeting and measurement on the Adelphic platform. And we expect that number to increase as we move through 2022. One of the biggest drivers of our growth in both Q4 and the full year is our continued momentum in CTV. Contribution ex TAC from CTV has nearly tripled over the last two years and now represents nearly half of our overall mix. In 2021 74% of customers invested in - of our customers invested in CTV on our platform. Contribution ex TAC from CTV grew 66% in Q4 and represented 45% of total contribution ex TAC during the quarter, far outpacing market growth rates for this segment of digital advertising. For the full year, contribution ex TAC from CTV grew 68% and represented 40% to 41% of the total. We also saw solid growth in the quarter across mobile, streaming audio and digital out of home channels. We expect these trends to continue as our people based targeting approach, along with the performance and measurement capabilities of our software platform are uniquely suited to drive return on ad spend for our customers in these channels. On the customer front, the number of active customers and the average contribution ex TAC per active customer continued to show strong momentum in the quarter. At the end of Q4 we had 309 active customers versus 264 in the prior year period, representing an increase of 45 customers in the year, up 40 - up 17% year-over-year. The biggest driver of new customer additions is our continued success with mid market agencies, which represented approximately two thirds of the customer additions over the period. Despite strong additions in new customers in Q4, nine political and auto customers from last year did not spend at all in 2021, and then - and therefore fell out of our customer count in Q4. The roll off of political customers is due to the lack of an election cycle in 2021. And the roll off of auto customers is tied to the supply chain issues we discussed. With the exception of the loss of these nine customers, our addition of new active customers in Q4 is in line with the growth we saw in Q2 and Q3. Average contribution ex TAC per active customer at the end of Q4 totaled $458,000 versus 419,000 at the end of 2020, representing a year-over-year increase of 9%. As we continue to ramp sales, marketing and technology investment in 2022 and beyond, we expect continued momentum around new customer acquisitions, and average contribution ex TAC tech per active customer. In Q4, we also continue to see the benefit of customers increasing spend the longer they are on the platform, what we call the cohort effect. In 2021, our top 50 customers that have been on the platform for at least one year increased spending by nearly 50%. The number of active customers spending at least $1 million per year also increased by 52% in 2021. Growth in the number of new customers and increase spending from existing customers coupled with 90 plus percent customer retention rates positions us extremely well for an acceleration of growth going forward, and affirms that the capabilities and performance of our software platform are resonating with marketers and their agencies in this fast growing programmatic advertising landscape. Tuning now to operating expenses. Adjusted cash operating expenses, which represents the difference between contribution ex TAC and adjusted EBITDA totaled $31.1 million in the quarter and $104.4 million for the full year, representing year-over-year increases of 32% and 33% respectively. The increases for both the quarter and the full year are primarily attributable to the planned investments we made across the organization, with a particular emphasis on ramping our sales, marketing and technology infrastructure. In 2021, we increased our total headcount by approximately 20%. We continue to attract extremely qualified candidates, and added many incredibly experienced new members to our team in 2021. I will talk more about this in a minute, but we intend to continue growing the team in '22 to further accelerate growth and advertiser spend across the platform to drive market share increases. Despite our under investment in 2021 relative to plan, we far exceeded our original estimates for revenue, contribution ex TAC and new customer wins, which speaks to the increased momentum we are seeing across the platform. Adjusted EBITDA for the quarter was $17.4 million and our adjusted EBITDA margin as a percent of contribution ex TAC was 36% for the quarter. For the full year, adjusted EBITDA was $37.1 million and our adjusted EBITDA margin was 26%. For the quarter, non-GAAP net income, which excludes stock based comp, totaled $13.4 million and non-GAAP earnings per Class A share totaled $0.17 for the quarter. For the full year, non-GAAP net income totaled $23.9 million and non-GAAP earnings per Class A share totaled $0.30. From a cash flow perspective, we generated $28.7 million of net cash from operating activities in 2021, an increase of 52% over 2020. And we ended the year with $238 million in cash, or approximately $4 per share outstanding. We expect to put some of this cash to work in the future opportunistically using M&A to deepen and expand our capabilities for our customers. That being said, we do recognize the current capital market environment and plan to be judicious in the use of our cash. We also ended the year with a modest amount of debt totaling $17.5 million and significant availability under our line of credit. We believe that our growth profile and healthy balance sheet position us extremely well to take advantage of the rapidly growing market opportunity in front of us. In terms of share count, we ended the year with 13.7 million [ph] in Class A common shares outstanding and 60.8 million total shares outstanding. For the end of 2022, we expect the Class A common share count to increase approximately 15.6 million and total shares outstanding to increase to approximate 62.3 million. The expected increases are primarily the result of vesting activity under our long term incentive plan. Before I discuss our guidance for 2022, I do want to point out that we have simplified the metrics for which we are giving guidance this quarter. We are eliminating guidance for contribution ex TAC, focusing on what we believe to be the two most important metrics by which we should be measured going forward, revenue and adjusted EBITDA. Given that our percent of spend pricing option is expected to drive most of our growth going forward, contribution ex TAC will become less important over time. We will however continue to report periodically on contribution ex TAC going forward. For modeling purposes, we expect growth rates for contribution ex TAC to be similar to growth rates for revenue in 2022. With that, I'll now turn to our guidance for Q1 and full year 2022, as well as our long term outlook. As Tim discussed, we feel great about our strength and positioning. We are in the very early stages of capitalizing on a fast growing market opportunity for programmatic advertisers. For the first quarter, we expect advertisers spend across our platform to further accelerate with growth of at least 35% compared to 9% in Q1 of 2021, and most recently 26% in Q4 2021. Q4 is obviously our biggest quarter of the year. We expect revenue in the range of $42 million to $44 million, which represents year-over-year growth of approximately 5% to 10%. And negative adjusted EBITDA on the range of $4 million to $5 million, as Q1 is our industry seasonally lowest volume quarter. And for the full year 2022, we expect advertisers spend across our platform to further accelerate with growth of at least 35% compared to 29% in 2021. We expect revenue in the range of $260 million to $270 million, which represents year-over-year growth of approximately 16% to 20% and adjusted EBITDA in the range of $25 million to $35 million. We have also included longer term targets in our earnings release today. These targets represent what we expect to achieve by 2025. By 2025, we expect revenue of at least $500 million, which represents a four year CAGR of at least 22%. We expect adjusted EBITDA margins as a percentage of contribution ex TAC at least 35%. Before concluding, I would like to make a few points relative to our guidance and the investments we are making. First in terms of Q1 and full year 2022 guidance, as I said, we expect to continue to gain market share in Q1, as advertisers spend on the platform is expected to accelerate from Q4 levels and increase by at least 35%., well in excess of the overall growth rates expected for the US programmatic market. We are seeing a faster than expected acceleration of growth across our percent of spend pricing option, which is far outpacing growth from fixed price. And increasing number of new customers are now going straight to percent of spend. And existing percent of spend customers are growing their spend at increasing rates, which we believe will provide for continued outside growth in spend across the platform going forward. As we've said before, the lifetime value of a customer using our percent of spend pricing option is significantly greater than that of a fixed price customer. As percent of spend customers ramp spend more significantly over time and have higher retention rates. On a short term basis, as we increase our market share by attracting more customer spend on our platform in our percentage spent pricing option. This dynamic is putting a drag on our revenue growth rates in Q1 and full year 2022 for that matter, as revenue from percent of spend is recorded after traffic acquisition costs, whereas fixed price revenue is recorded before deducting TAC. Percent of spend clients have higher retention rates, spend significantly more over time, and require less sales efforts to drive growth once fully ramped on the platform versus a fixed price customer. Ultimately percent of spend is a more consistent and predictable growth driver, given the cohort effect we've spoken off. Our fixed pricing up - fixed price pricing option, were more profitable than percentage of spend is more meant as an option for customers to test our software before transitioning to a longer term agreement with us. While this creates some short term pain in terms of revenue growth rates, we believe it better positions us for long term value creation and market share gains. Given the lower revenue base in Q1 due to seasonality, this trend is especially magnified in terms of revenue growth rates in the quarter. We expect revenue growth rates to improve beginning in Q2, as overall spend levels grow from Q1 levels. As a reminder in Q1 of last year, we grew revenue by 5% in the first quarter and finished the year with total revenue growth of 36%. In terms of planned investments and the impact on 2022 expected results, as Tim mentioned, we – intend to continue investing in critical areas of our business in 2022, to further accelerate growth and advertisers spend across our platform and drive market share. The wide range of EBITDA guidance for 2022 is in part based on the fact that our level of investment in '22 will ultimately be determined based on market conditions and other factors that we will closely monitor as the urine unfolds. So in terms of investment for 2022, we expect adjusted cash operating expenses to increase approximately 29% to 33% in 2020, roughly two thirds of the expense increase will come on the personnel side with half coming from the annualization of 2021 headcount additions, and half coming from new headcount investment in 2022. We expect to increase our headcount in 2022 by approximately 20%, which would put us north of 400 heads by the end of the year. Increased cloud costs supporting the support - supporting the growth in advertiser spend is also expected to increase total expense in 2022. We expect to ramp up our investment in automation initiatives, as well as to further build upon the ease of use of our software, which is critical to scaling customer spend. We will also be investing in marketing partnership initiatives and 22 to further increase the awareness of our solution in the marketplace. We believe these incremental investments, although impacting EBITDA in the short term will further accelerate our growth and market share gains going forward. Beyond 2022, we expect investment to become more normalized, as we charge towards our target of 35% EBITDA margins by 2025. In closing, our focus is on building a sustainable and profitable business for the future. As part of that, we will continue to make investments to increase our scale, so we can capture a meaningful share of this fast growing market. We have the utmost confidence that we can consistently grow our market share going forward, as our solution is increasingly resonating with marketers. As cookies and device IDs continue to become less and less prevalent, we believe that we are positioned for outside growth for many years to come. Our conviction is centered around how marketers and agencies are responding to our solution today, as evidenced by the acceleration in advertisers spend that we are seeing across the platform going into 2022. Our total addressable market is massive. And we firmly believe that our solution uniquely and effectively addresses many of the challenges that marketers are facing in today's digital - today's dynamic digital landscape. That concludes [ph] our prepared remarks today. And with that, I will now turn it back over to the operator to open the lines of questions. Operator?