The Node.js Event Loop Explained: From First Principles to Advanced Patterns
Introduction The Node.js event loop is the beating heart of every Node application. It powers non-blocking I/O, orchestrates timers, resolves promises, schedules callbacks, and coordinates the thread pool. Understanding it deeply is the difference between apps that feel crisp and resilient under load, and apps that stall, leak resources, or starve I/O. This tutorial takes you from beginner-friendly mental models to advanced, production-grade techniques. You’ll learn what the event loop is, how it’s implemented (libuv), the phases and microtask semantics, how timers work, how to measure and improve event loop health, and how to avoid common pitfalls like starvation and blocking. By the end, you’ll be comfortable reasoning about execution order, building reliable async flows, and tuning performance with confidence. ...