One post tagged with "database"

Every coding agent on Fibe — a "Genie" — runs as a Docker Compose project on someone's Marquee. When a Player clicks "start," we want one thing to be unambiguously true: at most one live Genie chat per agent on that host. Not "usually one." Not "one, unless two browser tabs fire at the same millisecond." One.

The interesting part isn't the rule. It's that we enforce it in two completely independent places — the application layer reuses the existing chat, and the database has a unique index that physically cannot hold two — and that this redundancy is the point, not an oversight. Here's why, and what leaning on a real invariant buys you downstream.