[ulfjack]

I work on Bazel.

We've put a bunch of work into making sure that we know about every file that goes into the Java compilation, and if any of them changes (and only then) do we recompile. Within Google, we use a form of sandboxing to enforce that.

You're also right that it isn't free - we have reason to believe that larger projects and larger teams will see benefits from using Bazel. Use your best judgement.