A:
Common structure:
- src/main.rs — Rocket setup, attach routes, launch
- src/routes/… — route handler modules
- src/models/… — Diesel schema, struct models
- src/db/… — connection pool setup (e.g. r2d2 + PgConnection)
- src/errors/… — error types and conversion
- src/migrations/… — Diesel migrations
This modular separation helps scale, testing, and readability.
