Domain Web

This kicks in when you're building web services in Rust, whether that's REST APIs, GraphQL endpoints, or WebSocket servers. It covers the domain constraints that matter for web development: why handlers must be async (blocking one task blocks many requests), how to manage shared state with Arc and RwLock, and proper request lifecycle patterns. You get framework comparisons between axum, actix, warp, and rocket, plus the critical patterns like extractors for parsing requests and IntoResponse for unified error handling. The focus is on tracing down from web-specific constraints (stateless HTTP, concurrency, latency SLAs) to concrete Rust implementations. Most useful when you need to understand why web frameworks work the way they do, not just copy-paste handler examples.