Consolidated Statements of Operations and Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Revenue	$ 34,339	$ 32,027	$ 31,098
Cost of revenue	16,132	16,387	15,316
Gross profit	18,207	15,640	15,782
Operating expenses
Research and development	7,244	6,468	7,331
Selling, general and administrative	7,265	6,777	6,636
Total operating expenses	14,509	13,245	13,967
Income from operations	3,698	2,395	1,815
Other income - net	218	54	229
Income before income taxes	3,916	2,449	2,044
Income tax provision	574	255	159
Net income	$ 3,342	$ 2,194	$ 1,885
Net income per share:
Basic	$ 0.19	$ 0.13	$ 0.11
Diluted	$ 0.19	$ 0.12	$ 0.10
Weighted-average shares outstanding used in computing net income per share:
Basic	17,587,804	17,283,133	16,982,648
Diluted	17,929,541	17,875,971	17,991,131
Comprehensive income:
Net income	$ 3,342	$ 2,194	$ 1,885
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on available-for-sale debt securities, net of tax of $11 for year ended December 31, 2020	56	(15)
Comprehensive income	$ 3,398	$ 2,179	$ 1,885