This repository is the source code for NGINX, a production-grade web server, reverse proxy, load balancer, API gateway, and mail proxy. The codebase is written entirely in C and is a definitive example of high-performance systems architecture. It employs a modular, event-driven, multi-process (master/worker) model. The core infrastructure is built around a set of highly optimized, self-contained data structures and utilities: a slab allocator for shared memory, a memory pool for request-scoped allocation, a red-black tree for timers and caches, a radix tree for IP routing, a hash table with wildcard support for server name matching, and an incremental JSON parser. The build system (auto/) is a sophisticated set of shell scripts that handle platform detection, dependency configuration, and module compilation. The code supports HTTP/1.x, HTTP/2, HTTP/3 (QUIC), TCP/UDP proxying (Stream module), and mail protocols (POP3, IMAP, SMTP). It is actively maintained, with a strong focus on performance, stability, and security. The code is exceptionally clean and well-structured for a project of its age and complexity, though it contains some platform-specific #ifdef sprawl and duplication between HTTP and Stream modules (e.g., upstream least_time, map).