Rust Web Services

Build Rust HTTP services with explicit state, typed boundaries, observable behavior, and production-grade runtime contracts.

Operating Model

1. Read the existing service shape first: router setup, app state, middleware layers, config, database access, tests, deployment scripts, and observability.
2. Prefer axum plus tower layers for new HTTP services unless the repo already standardizes on another framework.
3. Keep handlers thin. Extract inputs, call domain/service code, map results into HTTP responses.
4. Make app state explicit and clone-cheap. Avoid hidden globals and ad hoc connection creation per request.
5. Treat errors, tracing, timeouts, request size limits, and shutdown as part of the feature, not afterthoughts.

Reference Map

• references/axum-tower-architecture.md for router structure, state, extractors, middleware, errors, and versioned APIs.
• references/runtime-config-data.md for Tokio runtime concerns, config, database access, background jobs, and graceful shutdown.
• references/testing-observability.md for integration tests, tracing, metrics, contract tests, and production readiness.

Defaults

• Use tokio with only required features unless the repo uses full feature sets consistently.
• Use serde DTOs at HTTP boundaries and domain types internally.
• Use thiserror for domain errors and typed response mapping at the HTTP edge.
• Use tracing/tracing-subscriber with structured spans and request IDs.
• Use sqlx for database-backed services when compile-time query checking and async pooling are useful.

Verification

For service changes:

cargo fmt --all --check
cargo test --all-targets
cargo clippy --all-targets --all-features -- -D warnings

Add integration tests for new routes, error status mapping, auth/authorization branches, config parsing, database behavior, and graceful shutdown or background work when touched.