How Nginx’s Multi‑Process and Event‑Driven Architecture Powers High‑Performance Servers

Nginx is a core component of large‑scale architectures. It uses a classic Master‑Worker model where a single master process manages multiple worker processes, each handling requests independently, enabling true parallelism and high throughput.

Modern servers with multiple CPU cores can schedule each worker to a different core, allowing simultaneous execution of many connections.

Event‑driven architecture

Unlike traditional synchronous‑blocking models such as Apache’s prefork, Nginx’s workers run a single event loop that registers I/O events with the operating system. When an event (e.g., data arrival) is ready, the kernel notifies the worker, which then processes the connection.

This design lets a few worker processes efficiently handle thousands of concurrent connections.

I/O multiplexing

Workers use system calls like Linux’s epoll or FreeBSD’s kqueue to monitor multiple file descriptors. The call blocks until any registered I/O event becomes ready, after which the kernel returns the list of ready descriptors.

Non‑blocking I/O

When a worker initiates an I/O operation and the data is not yet available, the system call returns immediately with errors such as EAGAIN or EWOULDBLOCK. The worker then proceeds to other ready events, resuming the operation only when notified.