The four layers.

Codemojex stands on four layers, and each keeps the job the course gave it. The floor is Postgres: the record of truth for money, for a game’s secret and its commitment, and for game state, durable and constrained. Money is real and a game hides a secret, so both must survive a restart and stay auditable, which is why they live here and nowhere else as a source.

Above the floor sits EchoStore, a read-hot cache: a game’s secret and its emoji set do not change for the game’s life, so they are held in memory under the game’s version and read without touching Postgres on the hot path, falling back to the floor on a miss. Above that, EchoMQ on Valkey carries the real-time work — the per-player guess lanes, the leaderboard, the locks, the tier claims — all of it derived from the floor and the guesses, and all of it reconstructable.

At the top, Phoenix is the surface: a JSON and channel API behind privacy-safe views, and an operator console. Nothing above the floor is a second source of truth; the cache can be dropped and refilled, and the real-time tier can be rebuilt from the record. The reference implementation places money and the secret on the floor and treats everything above it as a fast, disposable view.