X0306 4 2021-03-15 0 0001490892 CoreSite Realty Corp COR 0001733571 Jones Mark R C/O CORESITE REALTY CORPORATION 1001 17TH STREET, SUITE 500 DENVER CO 80202 0 1 0 0 Chief Accounting Officer Common Stock 2021-03-15 4 A 0 2934 0.00 A 14458 D Common Stock 2021-03-15 4 S 0 140 115.76 D 14318 D Common Stock 2021-03-15 4 S 0 320 116.87 D 13998 D Common Stock 2021-03-15 4 S 0 622 117.91 D 13376 D Represents restricted stock granted under the issuer's Amended and Restated 2010 Equity Incentive Award Plan (the "2010 Plan"). The restricted stock vests in three equal annual installments beginning on March 15, 2022, provided that the reporting person remains in continuous service with the issuer as of each vesting date. The shares were sold pursuant to a sales plan adopted by the reporting person and intended to comply with Rule 10b5-1 under the Securities Exchange Act of 1934. Represents shares sold by the reporting person to cover tax obligations upon the vesting of restricted stock. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $115.18 to $116.17, inclusive. The reporting person undertakes to provide to the issuer, any shareholder of the issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnotes 5 through 7. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $116.40 to $117.36 inclusive. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $117.52 to $118.42, inclusive. /s/ Derek S. McCandless, Attorney-in-Fact 2021-03-17