Balance Sheet Components

Inventory

Inventory consists of the following (in thousands):



	January 31,
	2018		2019
Raw materials	$	1,181	$	3,349
Finished goods	33,316		41,338
Inventory	$	34,497	$	44,687

Property and Equipment, Net

Property and equipment, net consists of the following (in thousands):



	January 31,
	2018			2019
Test equipment	$	142,311		$	170,930
Computer equipment and software	72,329			117,330
Furniture and fixtures	5,363			6,980
Leasehold improvements	15,032			34,286
Total property and equipment	235,035			329,526
Less: accumulated depreciation and amortization	(145,893		)	(204,173		)
Property and equipment, net	$	89,142		$	125,353

Depreciation and amortization expense related to property and equipment was $48.8 million, $60.2 million and $68.3 million for the years ended January 31, 2017, 2018 and 2019, respectively.

Intangible Assets, Net

Intangible assets, net consist of the following (in thousands):



	As of January 31, 2018							As of January 31, 2019
	Gross Carrying Value		Accumulated Amortization			Net Carrying Amount		Gross Carrying Value		Accumulated Amortization			Net Carrying Amount
Technology patents	$	10,125	$	(5,068	)	$	5,057	$	10,125	$	(6,572	)	$	3,553
Developed technology	—		—			—		17,700		(1,135		)	16,565
Intangible assets, net	$	10,125	$	(5,068	)	$	5,057	$	27,825	$	(7,707	)	$	20,118

Intangible assets amortization expense was $1.4 million, $1.5 million and $2.6 million for the years ended January 31, 2017, 2018 and 2019, respectively. As of January 31, 2019, the weighted-average remaining amortization period was 2.4 years for technology patents and 6.6 years for developed technology. Amortization of the technology patents is included in general and administrative expenses due to their defensive nature and amortization of developed technology is included in cost of product revenue in the consolidated statements of operations.

As of January 31, 2019, future expected amortization expense for intangible assets is as follows (in thousands):



Fiscal Years Ending January 31,	Estimated Future Amortization Expense
2020	$	4,032
2021	4,032
2022	3,074
2023	2,529
2024	2,529
Thereafter	3,922
Total	$	20,118

Goodwill

The change in the carrying amount of goodwill is as follows (in thousands):



	Amount
Balance as of January 31, 2018	$	—
Goodwill acquired	10,997
Balance as of January 31, 2019	$	10,997

Accrued Expenses and Other Liabilities

Accrued expenses and other liabilities consist of the following (in thousands):



	January 31,
	2018		2019
Taxes payable	$	4,052	$	7,146
Accrued marketing	5,928		6,173
Accrued travel and entertainment expenses	4,386		3,570
Acquisition consideration held back	—		3,725
Other accrued liabilities	12,783		19,246
Total accrued expenses and other liabilities	$	27,149	$	39,860