CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Treasury Stock	Accumulated Deficit	Accumulated Other Comprehensive Loss
Redeemable Convertible Preferred Stock, beginning balance (in shares) at Oct. 01, 2016	32,482,590
Redeemable Convertible Preferred Stock, beginning balance at Oct. 01, 2016	$ 90,341
Redeemable Convertible Preferred Stock, ending balance (in shares) at Sep. 30, 2017	32,482,590
Redeemable Convertible Preferred Stock, ending balance at Sep. 30, 2017	$ 90,341
Balances, beginning of period (in shares) at Oct. 01, 2016		54,841,214		(7,780)
Balances, beginning of period at Oct. 01, 2016	(28,788)	$ 55	$ 144,771	$ (145)	$ (173,790)	$ 321
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net exercise of Series C preferred stock warrants (in shares)		742,034
Net exercise of Series C preferred stock warrants	10,078	$ 1	10,077
Exercise of stock options (in shares)		3,756,088
Issuance of common stock pursuant to equity incentive plans	8,906	$ 3	8,903
Retirement of treasury stock	(10,016)			$ (10,016)
Purchase of treasury stock (in shares)				(738,682)
Purchase of treasury stock	0
Stock-based compensation expense	36,550		36,550
Net loss	(14,217)				(14,217)
Change in foreign currency translation adjustment	(2,486)					(2,486)
Balances, ending of period (in shares) at Sep. 30, 2017		59,339,336		(746,462)
Balances, ending of period at Sep. 30, 2017	$ 27	$ 59	200,301	$ (10,161)	(188,007)	(2,165)
Increase (Decrease) in Temporary Equity [Roll Forward]
Conversion of redeemable convertible preferred stock upon initial public offering (in shares)	(32,482,590)
Conversion of redeemable convertible preferred stock upon initial public offering	$ (90,341)
Redeemable Convertible Preferred Stock, ending balance (in shares) at Sep. 29, 2018	0
Redeemable Convertible Preferred Stock, ending balance at Sep. 29, 2018	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common, net of issuance/offering costs (in shares)		6,388,888
Issuance of common, net of issuance/offering costs	86,027	$ 6	86,021
Conversion of redeemable convertible preferred stock upon initial public offering (in shares)		32,482,590
Conversion of redeemable convertible preferred stock upon initial public offering	90,341	$ 33	90,308
Exercise of stock options (in shares)		2,657,436
Issuance of common stock pursuant to equity incentive plans	9,345	$ 3	9,342
Purchase of treasury stock (in shares)				(60,578)
Purchase of treasury stock	(911)			$ (911)
Stock-based compensation expense	38,645		38,645
Net loss	(15,604)				(15,604)
Change in foreign currency translation adjustment	$ 488					488
Balances, ending of period (in shares) at Sep. 29, 2018	100,061,210	100,868,250		(807,040)
Balances, ending of period at Sep. 29, 2018	$ 208,358	$ 101	424,617	$ (11,072)	(203,611)	(1,677)
Redeemable Convertible Preferred Stock, ending balance (in shares) at Sep. 28, 2019	0
Redeemable Convertible Preferred Stock, ending balance at Sep. 28, 2019	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	7,925,897	8,755,167
Issuance of common stock pursuant to equity incentive plans	$ 31,574	$ 9	31,565
Purchase of treasury stock (in shares)				(213,735)
Purchase of treasury stock	(2,426)			$ (2,426)
Stock-based compensation expense	46,575		46,575
Net loss	(4,766)				(4,766)
Change in foreign currency translation adjustment	$ 1,613					1,613
Balances, ending of period (in shares) at Sep. 28, 2019	108,602,642	109,623,417		(1,020,775)
Balances, ending of period at Sep. 28, 2019	$ 280,928	$ 110	$ 502,757	$ (13,498)	$ (208,377)	$ (64)