The reconciliation of cash, cash equivalents and restricted cash reported in the accompanying unaudited condensed consolidated balance sheets to the total of the same such amounts in the accompanying unaudited condensed consolidated statements of cash flows is as follows (in thousands):


	March 31, 2022		December 31, 2021
Cash and cash equivalents	$	635,025	$	620,813
Restricted cash included in other assets	4,258		4,237
Total cash, cash equivalents and restricted cash	$	639,283	$	625,050


	March 31, 2022		December 31, 2021
Accounts receivable	$	652,529	$	521,597
Allowance for doubtful accounts	(392)		(132)
Product sales rebate and returns reserve	(3,531)		(4,956)
Accounts receivable, net	$	648,606	$	516,509


	March 31, 2022		December 31, 2021
Raw materials	$	367,811	$	316,737
Finished goods	326,406		333,380
Total inventories	$	694,217	$	650,117


	March 31, 2022		December 31, 2021
Inventory deposits	$	95,608	$	46,311
Prepaid income taxes	692		8,977
Other current assets	217,363		163,916
Other prepaid expenses and deposits	24,774		18,531
Total prepaid expenses and other current assets	$	338,437	$	237,735


	March 31, 2022		December 31, 2021
Land	$	40,336	$	40,145
Equipment and machinery	104,096		90,915
Computer hardware and software	44,792		44,083
Furniture and fixtures	3,638		3,634
Leasehold improvements	30,512		30,502

Construction-in-process	2,354		2,378
Property and equipment, gross	225,728		211,657
Less: accumulated depreciation	(138,337)		(133,023)
Property and equipment, net	$	87,391	$	78,634

Depreciation expense was $5.6 million and $4.9 million for the three months ended March 31, 2022 and 2021, respectively.


	March 31, 2022		December 31, 2021
Accrued payroll-related costs	$	47,799	$	99,571
Accrued manufacturing costs	92,197		80,213
Accrued product development costs	28,897		22,188
Accrued warranty costs	12,325		10,414
Other	15,845		14,257
Total accrued liabilities	$	197,063	$	226,643

The following table summarizes the activity related to our accrued liability for estimated future warranty costs (in thousands):


	Three Months Ended March 31,
	2022		2021
Warranty accrual, beginning of period	$	10,414	$	9,314
Liabilities accrued for warranties issued during the period	4,392		3,456
Warranty costs incurred during the period	(2,481)		(2,727)
Warranty accrual, end of period	$	12,325	$	10,043

The following table summarizes the beginning and ending balances of our contract assets included in "Prepaid and other current assets" on the condensed consolidated balance sheets (in thousands):


	Three Months Ended March 31,
	2022		2021
Contract assets, beginning balance	$	24,388	$	16,380
Contract assets, ending balance	14,051		9,762

A contract liability is recognized when we have received customer payments in advance of our satisfaction of a performance obligation under a cancellable contract. The following table summarizes the activity related to our contract liabilities (in thousands):


	Three Months Ended March 31,
	2022		2021
Contract liabilities, beginning balance	$	93,382	$	85,957
Less: Revenue recognized from beginning balance	(8,248)		(7,913)
Less: Beginning balance reclassified to deferred revenue	(3,837)		(12,492)
Add: Contract liabilities recognized	17,125		14,913
Contract liabilities, ending balance	$	98,422	$	80,465

As of March 31, 2022 and December 31, 2021, $40.8 million and $38.7 million of our contract liabilities, respectively, were included in "Other current liabilities" with the remaining balances in "Other long-term liabilities" on the condensed consolidated balance sheets.

Deferred revenue is comprised mainly of unearned revenue related to multi-year post-contract support ("PCS") contracts, services and product deferrals related to acceptance clauses. The following table summarizes the activity related to our deferred revenue (in thousands):


	Three Months Ended March 31,
	2022		2021
Deferred revenue, beginning balance	$	929,312	$	650,827
Less: Revenue recognized from beginning balance	(128,136)		(107,442)
Add: Deferral of revenue in current period, excluding amounts recognized during the period	322,570		176,646
Deferred revenue, ending balance	$	1,123,746	$	720,031

Other performance obligations include unbilled contract revenue for services and product that will be recognized in future periods. As of March 31, 2022, other performance obligations of $180.0 million were comprised mainly of unbilled multi-year PCS contract amounts.

Revenue from total remaining performance obligations represents contract liabilities, deferred revenue and other performance obligations. As of March 31, 2022, approximately $1,402.2 million of revenue is expected to be recognized from remaining performance obligations, of which approximately 83% is expected to be recognized over the next two years and approximately 17% is expected to be recognized during the third to the fifth year.


	Three Months Ended March 31,
	2022		2021
Interest income	$	2,428	$	2,045
Unrealized gain on equity investments	28,497		—
Other income (expense), net	555		(470)
Total	$	31,480	$	1,575