Balance Sheet Components

Inventory

Inventory consists of the following (in thousands):



	January 31,
	2017		2018
Raw materials	$	3,003	$	1,181
Finished goods	20,495		33,316
Inventory	$	23,498	$	34,497

Property and Equipment, Net

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



	January 31,
	2017			2018
Test equipment	$	105,955		$	142,311
Computer equipment and software	54,521			72,329
Furniture and fixtures	4,494			5,363
Leasehold improvements	10,332			15,032
Total property and equipment	175,302			235,035
Less: accumulated depreciation and amortization	(93,607		)	(145,893		)
Property and equipment, net	$	81,695		$	89,142

Depreciation and amortization expense related to property and equipment was $31.0 million, $48.8 million and $60.2 million for the years ended January 31, 2016, 2017 and 2018, respectively.

Intangible Assets, Net

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



	January 31,
	2017			2018
Technology patents	$	10,125		$	10,125
Accumulated amortization	(3,565		)	(5,068		)
Intangible assets, net	$	6,560		$	5,057

Intangible assets amortization expense was $1.3 million, $1.4 million and $1.5 million for the years ended January 31, 2016, 2017 and 2018, respectively. The weighted-average remaining useful life of the technology patents is 3.4 years. Due to the defensive nature of these patents, the amortization is included in general and administrative expenses in the consolidated statements of operations.

As of January 31, 2018, expected future amortization expense for intangible assets is as follows (in thousands):



Year Ending January 31,	Estimated Future Amortization Expense
2019	$	1,504
2020	1,504
2021	1,504
2022	545
Total	$	5,057

Accrued Expenses and Other Liabilities

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



	January 31,
	2017		2018
Taxes payable	$	1,675	$	4,052
Accrued marketing	6,718		5,928
Accrued travel and entertainment expenses	2,235		4,386
Other accrued liabilities	11,069		12,463
Total accrued expenses and other liabilities	$	21,697	$	26,829