The following sections and tables provide details of selected balance sheet items (in thousands):

	As of
	October 31, 2021		January 31, 2021
Finished goods	$	11,169	$	11,057
Raw materials		3,027		1,176
Total inventory	$	14,196	$	12,233

	As of
	October 31, 2021		January 31, 2021
Customer relationships	$	4,067	$	4,827
Developed technology		274		424
Trade names		193		262
Total intangible assets	$	4,534	$	5,513

Amortization expense for acquired intangible assets was $0.3 million for each of the three months ended October 31, 2021 and 2020 and $1.0 million for each of the nine months ended October 31, 2021 and 2020.

	As of
	October 31, 2021		January 31, 2021
Deferred sales commissions, current	$	5,998	$	4,689
Prepaid expenses		4,456		3,152
Convertible note receivable (see "GTC" below)		1,729		1,605
Deferred inventory costs		387		381
Other current assets		1,025		395
Total other current assets	$	13,595	$	10,222

Deferred sales commissions, non-current	$	13,176	$	11,474
Other non-current assets		777		736
Total other non-current assets	$	13,953	$	12,210

Customer Acquisition Costs. Amortization expense for deferred sales commissions was $1.5 million and $1.0 million for the three months ended October 31, 2021 and 2020, respectively, and $4.3 million and $2.7 million for the nine months ended October 31, 2021 and 2020, respectively. To date, there have been no material impairment losses related to the costs capitalized.

Global Telecom Corporation (“GTC”). In December 2018, the Company invested $1.3 million in cash in GTC, a privately-held technology company, in exchange for a convertible promissory note that will convert to shares of GTC stock upon the occurrence of certain future events. The promissory note and accrued interest is due and payable upon the Company’s demand at any time after December 31, 2021. The Company has also partnered with GTC on certain research and development and inventory procurement activities. GTC is a variable interest entity for accounting purposes and the Company does not consolidate GTC into its financial statements because the Company is not the primary beneficiary. The Company’s maximum exposure to loss is equal to the carrying value of the convertible note receivable, including accrued interest.

Additionally, as of October 31, 2021 and January 31, 2021, the Company recorded prepaid inventory deposits to GTC of $0.7 million and $0.1 million, respectively. As of October 31, 2021 and January 31, 2021, the Company’s non-cancelable inventory purchase commitments to GTC were $0.6 million and zero, respectively.

	As of
	October 31, 2021		January 31, 2021
Payroll and related expenses	$	9,597	$	11,062
Regulatory fees and taxes		4,053		4,141
Short-term operating lease liabilities		3,415		3,831
Customer-related liabilities		2,053		1,262
Other		3,213		2,435
Total accrued expenses and other current liabilities	$	22,331	$	22,731