Why Java NIO Outperforms Blocking I/O: Building a Multi-Threaded Web Server

A software developer has published a detailed walkthrough explaining why adding more hardware fails to fix latency problems in blocking I/O Java servers. The article, Part 2 of an ongoing series, demonstrates how traditional blocking servers assign one OS thread per connection, wasting memory and CPU through idle threads and excessive context switching. To address this, the author rebuilds an HTTP server from scratch using Java's Non-Blocking I/O (NIO) model, which uses Channels, Buffers, and Selectors to handle multiple connections on far fewer threads. Unlike blocking I/O, NIO's read and write calls return immediately rather than freezing a thread while waiting for data. The piece also candidly covers the concurrency bugs encountered when implementing features that frameworks typically abstract away.