Book: System Design Pocket Guide: Fundamentals Also by me: Database Playbook My project: Hermes IDE | GitHub — an IDE for developers who ship with Claude Code and other AI coding tools Me: xgabriel.com | GitHub You walk into the system design loop. Forty minutes in, the interviewer draws three letters on the whiteboard: C, A, P. They ask you to pick two. You say "AP, because partitions happen and we need availability." They nod. Then they ask the question that separates the senior candidates from everyone else: "what about latency, when there's no partition?" That is the question. Not CAP. The follow-up. And if your answer is some variant of "well, eventual consistency is fine," the loop is over and you don't know it yet. CAP started as Eric Brewer's 2000 PODC keynote conjecture and was proven by Gilbert and Lynch in 2002 . It says that a distributed system cannot simultaneously guarantee consistency, availability, and partition tolerance. Fine. The trouble is the framing.…