X0306 4 2021-07-30 0 0001490892 CoreSite Realty Corp COR 0001598763 Smith Steven James C/O CORESITE REALTY CORPORATION 1001 17TH STREET, SUITE 500 DENVER CO 80202 0 1 0 0 Chief Revenue Officer Common Stock 2021-07-30 4 S 0 107 135.34 D 51541 D Common Stock 2021-07-30 4 S 0 3221 138.71 D 48320 D Common Stock 2021-07-30 4 S 0 2019 139.55 D 46301 D Common Stock 2021-07-30 4 S 0 88 140.45 D 46213 D 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. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $135.24 to $135.92, 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 2 through 5. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $138.08 to $139.065, inclusive. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $139.10 to $140.00, inclusive. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $140.205 to $140.51, inclusive. /s/ Derek S. McCandless, Attorney-in-Fact 2021-08-03