How to size runners for Docker builds

You are choosing a runner size for image builds.

Why it happens

Docker builds are usually cache- and network-bound rather than CPU-bound, so a larger runner often changes nothing.

How to fix it

1. 8 vCPU is enough for most images — check whether you are actually CPU-bound first
2. If layers are being rebuilt, fix the cache before touching the size
3. Use a remote builder so the size of the orchestrating runner stops mattering
4. Compile-heavy images are the exception and do benefit from more cores