Design the CI platform for three hundred engineers. Builds currently take forty minutes and the queue is twenty deep at 4pm.

Queue time and build time are separate problems with separate fixes, and most teams spend a quarter optimising the one that is not hurting. Size the fleet from arrival rate, then attack the build with caching and graph awareness.

Updated Sep 2026 · Grounded in researched DevOps, SRE and platform engineering interview loops, written to a senior-engineer editorial bar, and never padded to hit a word count.