Modern high-performance servers—whether NGINX, Node.js, Redis, Netty, or Envoy—achieve millions of concurrent connections not through raw CPU clock speeds, but through mechanical sympathy with the operating system kernel’s I/O subsystems.
A naive architecture allocating one OS thread per connection collapses under thread stack memory exhaustion and context-switching overhead (the classic C10K problem). Modern distributed systems overcome this by leveraging asynchronous event-driven I/O (epoll, kqueue) and kernel bypass/zero-copy primitives (sendfile, io_uring).
This module deconstructs the operating system mechanisms powering low-latency distributed systems: blocking vs. non-blocking sockets, epoll red-black trees and ready lists, page cache writeback dynamics, zero-copy data pipelines, and the lockless ring-buffer architecture of Linux io_uring.