3. Revenue Recognition The following table disaggregates revenue by type (in tho usands): Year Ended December 31, 2021 Platform Professional Services and Other Total Timing of revenue recognition Transferred over time $ 67,065 $ 4,922 $ 71,987 Transferred at a point in time 77,381 — 77,381 Total revenue $ 144,446 $ 4,922 $ 149,368 Year Ended December 31, 2020 Platform Professional Services and Other Total Timing of revenue recognition Transferred over time $ 44,754 $ 5,660 $ 50,414 Transferred at a point in time 48,010 — 48,010 Total revenue $ 92,764 $ 5,660 $ 98,424 Year Ended December 31, 2019 Platform Professional Services and Other Total Timing of revenue recognition Transferred over time $ 32,670 $ 5,570 $ 38,240 Transferred at a point in time 12,451 — 12,451 Total revenue $ 45,121 $ 5,570 $ 50,691 Contract Balances Contract Asse t s As described in “Note 2–Significant Accounting Policies,” professional services revenue is generally recognized ratably over the implementation period, beginning on the commencement date of each contract. Platform revenue is recognized as the services are delivered. Under A SC Topic 606, Revenue from Contracts with Customers , we record a contract asset when revenue recognized on a contract exceeds the billings. Our standard billing terms are monthly; however, the billings may not be consistent with the pattern of recognition, based on when services are performed. Contract assets were $1.0 million and $0.9 million as of December 31, 2021 and December 31, 2020 , respectively. Unearned Revenue Unearned revenue primarily consists of billings or payments received in advance of revenue recognition from subscription services and is recognized as revenue when transfer of control to customers has occurred. During the year ended December 31, 2021 , we recognized $0.5 million of revenue related to contracts that were included in unearned revenue at December 31, 2020 . During the year ended December 31, 2020 , we recognized $0.8 million of revenue related to contracts that were included in unearned revenue at December 31, 2019 . As of December 31, 2021 , our remaining performance obligations were approximately $40.0 million , approximately 42% of which we expect to recognize as revenue over the next 12 months , and substantially all of the remaining revenue will be recognized thereafter over the nex t 24 to 48 mo nths. These amounts only include contracts subject to a guaranteed fixed amount or the guaranteed minimum under variable contracts. Unrecognized revenue under contracts disclosed above do not include (1) Table Of Contents OLO INC. Notes to Consolidated Financial Statements 88