Nginx

Nginx (pronounced "engine-x") is a high-performance, open-source web server that can also be used as a reverse proxy, load balancer, mail proxy, and HTTP cache. Its architecture is event-driven and asynchronous, employing a master process and multiple worker processes. The master process manages the worker processes, handling configuration reloads and graceful shutdowns. Worker processes, typically one per CPU core, efficiently handle client connections using a non-blocking, I/O multiplexing approach (e.g., epoll on Linux). This design allows Nginx to handle tens of thousands of concurrent connections with minimal memory footprint and CPU usage, making it exceptionally scalable and performant. Nginx excels at serving static content directly and efficiently, but its reverse proxy capabilities are equally powerful. It can distribute incoming traffic across multiple backend servers, perform health checks on those servers, and cache responses to reduce load. Its configuration language is declarative and hierarchical, allowing for fine-grained control over routing, security (SSL/TLS termination), caching rules, and request manipulation. Trade-offs include a less flexible module system compared to some competitors and a steeper learning curve for complex configurations, though its core functionality is straightforward.