NET LOSS PER SHARE - Computation of Net loss per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator
Net loss	$ (12,949)	$ (10,353)	$ (6,815)	$ (3,642)	$ (3,954)	$ (3,185)	$ (30,117)	$ (10,781)
Denominator
Weighted-average shares outstanding used in computing net loss per share, basic and diluted	49,264,938			989,203			33,535,829	648,611
Net loss per share, basic and diluted	$ (0.26)			$ (3.68)			$ (0.90)	$ (16.62)