Summary of significant accounting policies - Disaggregation of revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Total revenue	$ 366,388	$ 269,132	$ 203,965
SaaS subscription and support and maintenance | Recurring Revenue
Disaggregation of Revenue [Line Items]
Total revenue	313,950	223,655	158,493
On‑premise subscription | Recurring Revenue
Disaggregation of Revenue [Line Items]
Total revenue	30,293	25,224	16,625
Subscription
Disaggregation of Revenue [Line Items]
Total revenue	344,243	248,879	175,118
Subscription | Recurring Revenue
Disaggregation of Revenue [Line Items]
Total revenue	344,243	248,879	175,118
Services
Disaggregation of Revenue [Line Items]
Total revenue	16,122	14,519	19,014
Services | Non-recurring Revenue
Disaggregation of Revenue [Line Items]
Total revenue	16,122	14,519	19,014
License
Disaggregation of Revenue [Line Items]
Total revenue	6,023	5,734	9,833
License | Non-recurring Revenue
Disaggregation of Revenue [Line Items]
Total revenue	6,023	5,734	9,833
Non‑subscription revenue | Non-recurring Revenue
Disaggregation of Revenue [Line Items]
Total revenue	$ 22,145	$ 20,253	$ 28,847
Minimum | Services
Disaggregation of Revenue [Line Items]
Service performance period	1 day
Maximum | Services
Disaggregation of Revenue [Line Items]
Service performance period	2 days