Revenue

12 Months Ended

Dec. 31, 2021

Revenue from Contract with Customer [Abstract]

Revenue

Revenue

Disaggregation of Revenue

The following table presents a summary of revenue:

	Year Ended December 31,
(in thousands)	2021		2020		2019
Subscription revenue	$	476,023	$	377,354	$	290,549
Perpetual license and maintenance revenue	50,333		50,594		54,173
Professional services and other revenue	14,774		12,273		9,864
Revenue	$	541,130	$	440,221	$	354,586

Concentrations

We sell and market our products and services through our field sales force that works closely with our channel partners, which includes a network of distributors and resellers, in developing sales opportunities. We use a two-tiered channel model whereby we sell our products and services to our distributors, which in turn sell to resellers, which then sell to end users. We derived 92%, 91% and 90% of revenue through our channel network in 2021, 2020 and 2019, respectively. One of our distributors accounted for 39%, 43% and 43% of revenue in 2021, 2020 and 2019, respectively. That same distributor accounted for 32% and 41% of accounts receivable at December 31, 2021 and 2020, respectively.

Contract Balances

We generally bill our customers in advance and accounts receivable are recorded when we have the right to invoice the customer. Contract liabilities consist of deferred revenue and include customer billings and payments received in advance of performance under the contract. In 2021, 2020 and 2019, we recognized revenue of $329.0 million, $274.3 million and $214.0 million, respectively, that was included in the deferred revenue balance at the beginning of each of the respective periods.

Remaining Performance Obligations

At December 31, 2021, the future estimated revenue related to unsatisfied performance obligations was $559.0 million, of which approximately 76% is expected to be recognized as revenue over the succeeding twelve months, and the remainder expected to be recognized over the four years thereafter.

Deferred Commissions

The following summarizes the activity of deferred incremental costs of obtaining a contract:

	Year Ended December 31,
(in thousands)	2021		2020
Beginning balance	$	78,876	$	72,265
Capitalization of contract acquisition costs	58,196		38,756
Amortization of deferred contract acquisition costs	(37,123)		(32,145)
Ending balance	$	99,949	$	78,876