Ensign Juan Cordova was a 23rd century Human man, a Starfleet security officer assigned to the Federation starship USS Enterprise in the 2260s decade.
In the year 2269, he accompanied David Steinberg and Zar on a mission to the planet Gateway, to evacuate the archaeologists from the threat of a Romulan attack. Unfortunately, Cordova was killed by a Romulan soldier. (TOS - The Yesterday Saga novel: Yesterday's Son)