7. Commitments and Contingencies Operating and Capital Leases The Company leases domestic office space in Arlington, Virginia and San Francisco, California, as well as international office space in Japan, Singapore, Ukraine and the United Kingdom. All leases are non-cancelable operating lease agreements that expire at various dates through 2018 and include renewal options. In June 2013, the Company entered into a master lease agreement with a financing company. The agreement allows for the Company to lease eligible equipment purchases. Each lease has a 36 month term, payable in equal monthly installments with the exception of the first and final payments which are prorated based on a midmonth convention. The Company has accounted for the leases under the master lease agreement as capital leases. The weighted-average interest rate implicit in the leases was 5.5%. A summary of lease commitments as of December 31, 2015 is as follows (in thousands): Year ending December 31, Operating Leases Capital Leases 2016 $ 5,663 $ 449 2017 2,804 63 2018 470  8,937 512 Less: Amounts representing interest  15 Total lease obligations $ 8,937 $ 497 Rent expense under operating leases was $5.5 million, $4.4 million, and $3.0 million for the years ended December 31, 2015, 2014 and 2013, respectively. Letters of Credit As of December 31, 2015 and 2014, the Company had outstanding letters of credit totaling $1.3 million in connection with securing its leased office space. The outstanding amounts for Arlington and San Francisco are $0.6 million and $0.7 million, respectively, and both letters of credit remain outstanding as of December 31, 2015. Contingencies and Indemnifications In the ordinary course of business, the Company enters into contracts and agreements that may contain representations and warranties and provide for general indemnifications. The Companys exposure under these agreements is unknown because it involves claims that may be made in the future, but have not yet been made. The Company has not paid any claims or bee