Tatu Mäkijärvi
About
Every minute added to a CI pipeline multiplies across:
- Pull requests per day
- Engineers on the team
- Context switches
- Interrupted flow states
A 12-minute pipeline in a team of 15 engineers running 6 builds per day equals 18 hours of waiting — every day.Speed in CI is not cosmetic. It is structural.At its core, caching in CI is the practice of persisting previously computed outputs and reusing them when the same inputs appear again. That sounds trivial, but the implications are structural.Every CI run performs a series of deterministic transformations: install dependencies, compile code, bundle assets, run tests, build containers. If the inputs to those steps have not changed, their outputs do not need to be recomputed. Instead, they can be restored.The entire discipline of CI caching rests on that single assumption: identical inputs produce identical outputs.
