SQLx: pools and checked queries

Most Rust backends talk to PostgreSQL through SQLx, which runs plain SQL asynchronously on Tokio. You create one PgPool, a pool of open connections, at startup and share it through your app state. Placeholders like $1 send values separately from the SQL text, which protects you from SQL injection.

The query! and query_as! macros check every query against a real database while the code compiles, so a misspelt column or a wrong type fails the build. cargo sqlx prepare saves that information to a .sqlx folder, so CI can build without a database. Diesel is the main alternative, a query builder and ORM with its own style.