The Delta Vega outpost was a Starfleet facility on the planetoid Delta Vega. Montgomery Scott and Keenser were assigned to this outpost for six months during the year 2258. Shuttle 78072 was docked there. A tribble was kept in a cage in the middle of Scotty's desk, which was littered with various pieces of equipment.
Following James T. Kirk's argument with Commander Spock, he was marooned on the planetoid by the Vulcan. After Kirk met up with the prime universe Spock, the two traveled a 14km distance to the outpost together.
Once inside, Keenser led them to Scotty. The engineer, believing their visitors to be making a supply run, bombarded them with complaints for not arriving sooner to restock the outpost's foodstuffs, as the lack of available food necessitated the consumption of less palatable protein nibs for the last six months. Spock Prime then entered what was apparently Scott's future formula for transwarp beaming into the computer of the outpost's derelict shuttle, impressing the engineer. (Star Trek)
The IDW Star Trek: Ongoing comic Keenser's Story revealed that Keenser's assignment to the outpost pre-dated Scott's. It also revealed that the facility originally had a larger staff, who had all transferred sometime prior to Scott's assignment there.