What Is a Compiler Cache?

A compiler cache is a layer in front of a compiler that records the output for a given set of inputs and replays it when the same inputs recur. The cache key captures the source, compiler version, and flags so a hit is guaranteed to match what a real compile would produce. Tools like ccache and sccache implement this idea.

Why it matters

Compilation is often the longest part of a build, and most of it is repeated work across commits and runners. A correct compiler cache converts that repeated work into cheap lookups, shrinking both build time and CI cost. The whole guarantee rests on the key including every input that can change the output.

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