X0306 4 2019-05-23 0 0001490892 CoreSite Realty Corp COR 0001183333 BUA JEAN A C/O CORESITE REALTY CORPORATION 1001 17TH STREET, SUITE 500 DENVER CO 80202 1 0 0 0 Common Stock 2019-05-23 4 M 0 1260 0.00 A 2510 D Restricted Stock Units 2019-05-23 4 M 0 1260 0.00 D Common Stock 1260 1502 D Each Restricted Stock Unit ("RSU") represents the right to receive one share of common stock of the issuer. The reporting person also holds a tandem dividend equivalent for each RSU held, which gives the reporting person the right to receive, upon the payment of any ordinary quarterly cash dividend paid to holders of common stock of the issuer, an equivalent payment in the form of additional RSUs based on the fair market value of the issuer's common stock on the date of payment. The RSUs vested in full on May 23, 2019. The RSUs have no expiration date. /s/ Derek S. McCandless, Attorney-in-Fact 2019-05-28