Summary of significant accounting policies (Tables)

9 Months Ended

Sep. 30, 2021

Revenue from subscription and non-subscription contractual arrangements are as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020 (1)		2021		2020 (1)
			(As Revised)				(As Revised)
	(in thousands)
SaaS subscription and support and maintenance	$	83,775	$	57,785	$	222,672	$	160,279
On‑premise subscription	6,925		7,849		23,228		18,159
Subscription revenue	90,700		65,634		245,900		178,438
Professional services	4,083		3,897		12,015		10,616
Perpetual licenses	838		1,017		4,671		3,811
Non‑subscription revenue	4,921		4,914		16,686		14,427
Total revenue	$	95,621	$	70,548	$	262,586	$	192,865

(1) Certain prior period amounts have been revised to correct immaterial errors. See Note 1 for more information.

Contract with Customer Asset and Liability

Changes in contract liabilities, including revenue earned during the period from the beginning contract liability balance and new deferrals of revenue during the period, were as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020 (1)		2021		2020 (1)
			(As Revised)				(As Revised)
	(in thousands)
Balance, beginning of the period	$	238,457	$	157,282	$	205,509	$	140,449
Acquisitions	5,200		—		5,200		—
Revenue earned	(71,574)		(49,823)		(144,038)		(115,784)
Deferral of revenue	98,284		80,179		203,696		162,973
Balance, end of the period	$	270,367	$	187,638	$	270,367	$	187,638

(1) Certain prior period amounts have been revised to correct immaterial errors. See Note 1 for more information.