The Bazel build system [1] is the open-source version of Google's internal build system. It's tough to set up, but once you do - it caches all builds, down to the docker container generation. On changes, it analyzes affected upstream projects and selectively rebuilds them. So, after an initial build, rebuilds are blazingly fast. In fact, the simple act of creating a pull request means that most production builds/deploys come straight from cache.

Here [2] is a screenshot of the actual "master branch test, lint, build, and deploy 15 containers to kubernetes" job from our Jenkins. It took about 10 minutes on the build box every time.

That being said, in order to make builds work with Bazel, we had to do some wonky stuff. We committed built Javascript files, and we had to manually commit a lot of other types of data files (like bindata.go and protobuf outputs).

[1] http://bazel.build

[2] <I'll drop this in as soon as Imgur/S3 is back online . . . >