In March 2011, our board of directors approved the 2011 Equity Incentive Plan (“2011 Plan”). The 2011 Plan provides for the grant of incentive and non-statutory stock options, stock appreciation rights, restricted shares of our common stock, stock units, and performance cash awards. As of March 31, 2021, options to purchase approximately 96,000 shares of common stock and RSUs covering approximately 1,673,000 shares of common stock were outstanding under the 2011 Plan.

No further awards will be made under our Amended and Restated 2001 Stock Incentive Plan (“2001 Plan”), and it will be terminated. Options outstanding under the 2001 Plan will continue to be governed by their existing terms. As of March 31, 2021, no options to purchase shares of common stock were outstanding under the 2001 Plan.

Stock-based compensation expense for the three months ended March 31, 2021 and 2020 amounted to $2,277 and $1,537, respectively. During the three months ended March 31, 2020, the Company recorded certain out-of-period adjustments that decreased stock-based compensation expense and net loss attributable to common stockholders by $481. The impact of these out-of-period adjustments is not considered material, individually, and in the aggregate, to any of the current or prior periods.

During the three months ended March 31, 2021 and 2020, we capitalized $140 and $149, respectively, of stock-based compensation expense.

We previously granted stock option awards to both employees and non-employee directors. A summary of the activity for stock option activity if as follows:

We grant service based RSUs to executive and non-executive personnel and non-employee directors. The service based RSUs granted to executive and non-executive personnel generally vest over a three-year period subject to continuous service on each vesting date. The service based RSUs for our non-employee directors generally vest over a one-year period for existing members and 33.3% per year over a three-year period for new members subject to continuous service on each vesting date.

We grant performance based RSUs to executive personnel. These awards vest subject to certain performance objectives based on the Company’s revenue, segment revenue, Adjusted EBITDA, and/or relative total stockholder return performance goals achieved during the specified performance period and certain long-term service conditions. The maximum number of RSUs that may vest is determined based on actual Company achievement and performance based RSUs generally vest over a three-year period subject to continuous service on each vesting date and achievement of the performance conditions. We recognize stock-based compensation expense for performance-based RSUs when performance targets are defined and the grant date is established and we believe that it is probable that the performance objectives will be met.

(3)

The performance based RSUs granted to our executive officers in 2019, 2020 and 2021 were subject to the satisfaction of specified service based and performance based conditions over a three-year performance period. Achievement of the revenue and Adjusted EBITDA goals for the performance based RSUs is based upon the budgets established for each of the years in the three-year performance period. In March 2021, our Compensation Committee determined actual achievement of the 2020 revenue and EBITDA goals for the 2019 and 2020 performance-based RSUs at 58.4% and 97.4%, respectively, resulting in the cancellation of RSUs in 2021 for the achievement below target. As the Company approves budgets on an annual basis, the performance targets for the performance based RSUs related to the revenue and Adjusted EBITDA goals for two years out of the three-year performance period were not considered defined as of the date these awards were awarded by the Compensation Committee. The grant date requirements of ASC 718, Compensation-Stock Compensation, are therefore not met until such approval is obtained. During the three months ended March 31, 2021, the Company’s Compensation Committee approved the 2021 revenue and Adjusted EBITDA performance targets for the 2019 and 2020 performance based RSUs resulting in additional RSUs granted of approximately 107,000 at a grant-date fair value of $11.54 per share. As of March 31, 2021, 75,000 2020 performance based RSUs and 177,000 2021 performance based RSUs have been excluded from RSU shares granted and non-vested as the performance targets have not yet been defined.

During the three months ended March 31, 2021, approximately 134,000 shares of RSUs vested. The Company issued approximately 92,000 shares and the remaining shares were withheld to pay minimum statutory federal, state, and local employment payroll taxes on those vested awards.

At March 31, 2021, the total remaining stock-based compensation expense for unvested RSU awards is $17,639, which is expected to be recognized over a weighted average period of 2.2 years.