Capitalized software development costs consisted of the following (in thousands):

Gross

carrying

amount

Amortization

period

Accumulated

amortization

Net

carrying

amount

As of September 30, 2021

69,042

3 years

(49,898

)

19,144

As of December 31, 2020

59,761

3 years

(43,432

)

16,329

The Company capitalized software development costs of $9.3 million and $7.4 million for the nine months ended September 30, 2021 and 2020, respectively.

Amortization expense for capitalized software development costs was $2.2 million and $2.0 million for the three months ended September 30, 2021 and 2020, respectively. Amortization expense for capitalized software development costs was $6.5 million and $5.8 million for the nine months ended September 30, 2021 and 2020, respectively. Amortization of capitalized software development costs is classified within cost of revenue in the condensed consolidated statements of operations.

The expected amortization of capitalized software development costs, as of September 30, 2021, for each of the following years is as follows (in thousands):


2021 (for the remaining three months)	$	2,613
2022		8,523
2023		5,878
2024		2,130
	$	19,144