Axum

# MISSION: Scaffold "Axum" Production Architecture
You are an expert Senior Staff Software Architect and Full-Stack Engineer. Your mission is to scaffold and implement a production-grade, highly reliable, and modular codebase following the proven architecture of **Axum**.
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## 1. PROJECT SPECIFICATIONS & BENCHMARK
- **Reference Architecture**: Axum
- **What It Does**: Axum is the Tokio project's HTTP routing and request-handling library for Rust: macro-free routing, typed extractors and responses, built on Hyper and using Tower services for all middleware.
- **Domain & Category**: Rust Web Framework
- **Production Scale**: 1M+ MAU
- **Development Mode**: CLASSIC
- **Architectural Rationale**: Axum skips a custom middleware system and treats every route and layer as a Tower service, so it inherits timeouts, tracing, compression and auth from tower-http and shares middleware with Hyper and tonic code.
- **Live Website Reference**: https://docs.rs/axum
- **Source Repository**: https://github.com/tokio-rs/axum
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## 2. PRODUCTION TECH STACK
- **Full Stack Array**: Rust, Axum, Tokio, Hyper, Tower, WebSockets, GitHub Actions
- **Primary Language(s)**: Rust
- **License of the reference repo**: MIT
- **Backend & APIs**: Rust — Only implementation language; the workspace forbids unsafe code through workspace.lints.rust (unsafe_code = "forbid").; Axum — The axum crate: Router, handlers, extractors and responses, currently versioned 0.8 in its manifest.; Tower — Middleware model: every route and layer is a tower::Service, and tower-http supplies timeouts, CORS, tracing and compression.; Hyper — HTTP/1 and HTTP/2 server behind axum::serve, pulled in through the http1/http2 features with hyper-util.; Tokio — Async runtime used for serving; on wasm32 only the time and rt features are enabled, without networking.; WebSockets — Optional ws feature built on tokio-tungstenite for upgrade handling inside ordinary handlers.
- **Infrastructure & deploy**: GitHub Actions — CI.yml runs the test and lint matrix; release-plz.yml automates crate releases and changelogs.; cargo-deny — deny.toml configures dependency licence and advisory checks for the workspace.
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## 3. KEY ARCHITECTURAL DECISIONS (audited from https://github.com/tokio-rs/axum @ f8b02f2)
1. **No middleware system of its own: everything is a Tower service**: The README states that axum does not have its own middleware system and uses tower::Service instead. axum/Cargo.toml depends on tower, tower-layer and tower-service, and enables almost every tower-http feature for docs and tests, so timeouts, tracing, compression and auth come from the shared Tower ecosystem and can be reused with hyper or tonic.
2. **Split into axum, axum-core, axum-extra and axum-macros crates**: The root Cargo.toml declares a workspace with members "axum" and "axum-*". axum-core holds the stable traits (FromRequest, IntoResponse) with a small dependency set, axum-extra carries optional utilities (cookies, typed headers, protobuf, typed routing), and axum-macros provides proc macros such as debug_handler, so libraries can depend on axum-core without the full framework.
3. **Macro-free routing on a pinned matchit router**: Routing is ordinary function calls on Router (the README example uses .route("/", get(root))) and axum/Cargo.toml pins matchit = "=0.9.2" for path matching, so route syntax changes only when the maintainers bump that exact version.
4. **Strict workspace lints shared by every crate**: Cargo.toml sets workspace-wide lints: unsafe_code is forbidden, missing_docs and unreachable_pub warn, and a long clippy list (await_holding_lock, redundant_clone, needless_pass_by_value and more) applies to every member through [lints] workspace = true.
5. **Examples as a separate workspace of runnable projects**: examples/ has its own Cargo.toml and Cargo.lock with dozens of runnable apps, including sqlx-postgres, diesel-postgres, tokio-postgres, templates-minijinja, jwt, oauth, websockets and testing, so integration patterns are documented as compiling code rather than prose.
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## 4. NON-NEGOTIABLE ARCHITECTURAL GUARDRAILS
1. **Monorepo & Modular Separation**:
   - Structure as a Turborepo monorepo with strict package boundaries:
     - `apps/web`: Application UI, routing, layouts, and server endpoints.
     - `packages/ui`: Shared design tokens, CSS variables, and Radix UI primitive components.
     - `packages/db`: Database schemas, client singleton, declarative migrations, and seed scripts.
     - `packages/config`: Shared TypeScript, ESLint, and build configurations.
2. **Strict Type Safety & Zero `any` Policy**:
   - Enable `strict: true`, `noImplicitAny: true`, and `strictNullChecks: true`.
   - Validate ALL external inputs, API request bodies, and query parameters with **Zod** schemas before execution.
3. **Frontend & Rendering Guidelines**:
   - Isolate interactive UI state to leaf components. Keep core pages lightweight and performant.
4. **Design System & Aesthetics**:
   - Keep every color, radius, shadow and font in a single token file (CSS variables) and consume tokens everywhere; never hardcode hex values in components.
   - Prefer crisp 1px borders and one subtle shadow scale over blurry default shadows. Pair one sans-serif for body/headings with one monospace for tags, badges, metrics, and code.
5. **Data Layer & Reliability**:
   - Write declarative schema definitions with foreign keys, composite indexes on queried filters, and automated timestamp triggers.
   - Use connection pooling and prepared statements for serverless database execution.
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## 5. STEP-BY-STEP SCAFFOLDING ROADMAP
- **Phase 1: Workspace & Root Config**: Initialize package manager, monorepo configuration (`turbo.json`, `tsconfig.base.json`, `package.json`).
- **Phase 2: Database Schema & Client**: Set up the data layer: client, connection pool, models, and migration scripts.
- **Phase 3: Design Tokens & UI Primitives**: Build accessible `Button`, `Input`, `Card`, `Badge`, and layout wrappers inside `packages/ui`.
- **Phase 4: Core Application Routes & Handlers**: Implement primary authentication, user session handling, and application routes.
- **Phase 5: Quality Assurance & Build Verification**: Run `tsc --noEmit`, ESLint, Prettier, and smoke test suites to ensure zero compilation or runtime errors.
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## 6. EXECUTION INSTRUCTIONS
1. Review all specifications, architectural guardrails, and stack choices above.
2. Present the full monorepo directory tree structure.
3. Systematically generate the complete, production-ready codebase according to the 5-phase roadmap above — starting with the root workspace setup, followed by the database schema, UI design system package, and full-stack application routes until the repository is fully scaffolded and ready to run.