The Cache Hit That Wasn't
GitHub Actions claims sub-second cache restore times. GitLab CI promises distributed caching. I ran the same Node.js build 100 times on both platforms and found an 8.4-second gap that nobody talks about.
The test was simple: restore 400MB of node_modules, run tests, save cache. Same repo, same dependencies, same compute tier (2-core Linux runners). GitHub Actions averaged 2.1 seconds for cache restore. GitLab CI took 10.5 seconds.
That's a 5x difference before your actual CI job even starts.
Why This Matters for Real Builds
Every CI run hits cache at least twice: once to restore dependencies, once to save artifacts. If you're running 50 builds a day (modest for a team of 5-10), that 8-second gap costs you 7 minutes per day. Scale to 500 builds and you've lost over an hour of cumulative wait time.
But the real cost isn't the wall-clock time — it's context switching. Developers check build status 3-4 times during a typical PR. Each extra second is another mental reload.
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