# Contract Delta: 005-postgres-database-replacement

> For the complete documentation index, see [llms.txt](https://traderx.finos.org/llms.txt).

[Learning Guide — PostgreSQL Database Replacement](https://traderx.finos.org/docs/learning/state-005-postgres-database-replacement.md): purpose, walkthrough, and related learning states.

# Contract Delta: 005-postgres-database-replacement

Parent state: `004-containerized-compose-runtime`

## OpenAPI Changes

*   No REST OpenAPI contract changes.

## Event Contract Changes

*   No trade-feed Socket.IO event contract changes in this state.

## Compatibility Notes

*   UI-visible behavior and endpoint contracts are intentionally preserved.
*   Persistence backend contract changes are internal (SQL engine + init process) and do not change REST payload shapes.
*   Account sequence semantics are preserved using PostgreSQL `accounts_seq`.