Making It Fast: Caching, Hot Paths, and Avoiding DB Calls

The Auth Gateway sits in front of every authenticated request in the platform. Its latency isn't just its own latency — it's the floor for every service behind it. If auth takes 50ms, every request to every upstream service starts 50ms in the hole. Our internal target is sub-millisecond on cache-hot paths. The way we hit it isn't clever algorithms — it's a stack of small caches, each one handling a different kind of state, each invalidated through a different channel. This post walks through all