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

Gross

carrying

amount

Amortization

period

Accumulated

amortization

Net

carrying

amount

As of June 30, 2021

66,057

3 years

(47,689

)

18,368

As of December 31, 2020

59,761

3 years

(43,432

)

16,329

The Company capitalized software development costs of $6.1 million and $4.7 million for the six months ended June 30, 2021 and 2020, respectively.

Amortization expense for capitalized software development costs was $2.2 million and $1.9 million for the three months ended June 30, 2021 and 2020, respectively. Amortization expense for capitalized software development costs was $4.3 million and $3.8 million for the six months ended June 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 June 30, 2021, for each of the following years is as follows (in thousands):


2021 (for the remaining six months)	$	4,779
2022		7,630
2023		4,985
2024		974
	$	18,368