OCaml-CI is a CI service for OCaml projects. It uses metadata from the project’s opam and dune files to work out what to build, and uses caching to make builds fast. It automatically tests projects against multiple OCaml versions and OS platforms. The CI has been deployed on around 50 projects so far on GitHub, and many of them see response times an order of magnitude quicker than with less integrated CI solutions. This talk will introduce the CI service and then look at some of the technologies used to build it.