Axum Database Access with sqlx

Overview

An Axum service talks to a SQL database through a sqlx connection pool. The pool is an expensive resource: every connection is a real TCP socket (usually with TLS) plus a server-side session. The pool MUST be created exactly once at startup and shared with every handler through router state.

sqlx exposes the pool as Pool<DB>, with the type aliases PgPool for Postgres, MySqlPool for MySQL, and SqlitePool for SQLite. This skill uses Postgres; the patterns apply uniformly to the other databases by substituting the type.

Three rules dominate correct database code in Axum: