PGSimCity turns Postgres internals into an explorable 3D city

Nikolay Samokhvalov built PGSimCity, a walkable 3D model of Postgres internals, and it hit 888 points on Hacker News. It's aimed at engineers who run Postgres without ever operating a database. They're the ones who get paged when a checkpoint spikes latency, with no idea why.

The city's central plaza is shared_buffers: 1,024 individual page frames laid out as plots. Each plot's height tracks its clock-sweep usage count, its color shows the buffer's true state. Walk east and you hit an amber district, the WAL.

Below the plaza sits a pit, the data directory, where heap files visibly grow as you bloat them. A standby server sits south of the city, replaying whatever the primary sends. Always a step behind.

None of it runs real Postgres code, and Samokhvalov says so directly. It's a hand-written model, not an emulator. That's a real limit: nothing here proves the numbers match what happens under production load.

I like that he's upfront about it. My take: this will teach checkpoint latency and buffer eviction faster than the official docs ever have. It shows a heap file actually swell instead of describing a page write. If it ends up bookmarked in onboarding docs at a company running Postgres at scale, that bet pays off.