Backend with NestJS

Start with the vocabulary — controller, provider, module, decorator, and the one TypeScript line that wires them — then the three things a Nest codebase asks you to reason about: the module graph and the injector that connects providers, the DTO contract that decides what a handler is even allowed to receive, and the request lifecycle — pipes, guards, interceptors and exception filters — that runs around every handler. Then the production layer: how routes are matched, versioned and answered, caching and rate limits shared through Redis, and services that talk over messages that can arrive twice.