This page contains information regarding Star Trek: Discovery, and thus may contain spoilers.
DOT-7s were a type of worker robot in operation in the 2250s through the 2280s aboard Federation starships like the USS Enterprise. They were distinguished by a vaguely humanoid silhouette with a head and robotic manipulator arms, and, though they lacked legs, they possessed four maneuvering thrusters on their backs.
During the Battle near Xahea, several DOT-7s were deployed after an undetonated torpedo fired by a Section 31 ship became lodged in the Enterprise's forward section. (DIS: "Such Sweet Sorrow, Part 2")
By 2267, DOT-7s still operated aboard Constitution-class ships, distinguished by red markings and antler-like extensions on their heads. During this time a DOT-7, identified as Dot, had an extended interaction with a mycelial tardigrade, identified as Ephraim, that lasted from the 2260s to 2285. (ST: "Ephraim and Dot")
There is precedent for repair robots in the Fifteenth UK Story Arc, published in 1970. The experimental machines, on loan from a research depot on Venus, worked on the Enterprise in a story set between 2267 and 2269. Although more humanoid than DOT-7s, they possessed similar manipulator "hands".