Node.js Under the Microscope: What Senior Engineers Actually Know

By Vivek Kumar 3 min read

Node.js Under the Microscope: What Senior Engineers Actually Know

Most Node.js tutorials teach you how to build a server in 5 minutes. They cover express, routing, and basic database connections.

But what happens when your application hits production? What happens when 10,000 concurrent requests flood your system, the event loop lags, libuv’s threadpool exhausts, and memory usage explodes?

To scale Node.js genuinely, you must understand exactly how it works under the hood.

This series of 20 deep-dive articles strips away the abstractions. It covers what senior engineers need to know about the event loop, libuv, worker threads, backpressure, and the nuances of high-concurrency Node.js architecture.

Complete Series Index

Event Loop & Scheduling Mechanics

  1. Node.js Is Not Single-Threaded — And That Misconception Costs You Scale
  2. The Event Loop Is Just a Scheduler — Here’s What It Actually Schedules
  3. Inside libuv: The Hidden Engine Behind Node.js Scalability
  4. The 6 Phases of the Event Loop — And Why Most Engineers Misunderstand Them
  5. setTimeout(0) vs setImmediate(): The Interview Trap That Reveals Your Depth
  6. Microtasks, nextTick, and Promises: The Hidden Priority System in Node.js

Performance & System Bottlenecks

  1. How to Freeze 10,000 Users With One Line of Code in Node.js
  2. Threadpool Exhaustion: The Silent Killer of Node.js APIs
  3. Why Your Node.js API Is Slow Even When CPU Usage Is Low
  4. When NOT to Use Node.js — A Decision Framework for Backend Engineers
  5. Why Increasing UV_THREADPOOL_SIZE Can Make Your System Slower

Production Metrics & Debugging

  1. Event Loop Lag: The Metric That Matters More Than CPU
  2. How to Measure Event Loop Lag in Production (Without Guessing)
  3. Debugging Event Loop Lag in Production: A Playbook

Concurrency: Threads vs Processes

  1. Worker Threads vs Child Processes: The Real Tradeoffs Nobody Explains
  2. When to Use Worker Threads — And When They Make Things Worse

Managing Traffic at Scale

  1. What Happens When 10,000 Requests Hit a Node.js Server
  2. From Socket to Callback: The Full Journey of a Request in Node.js
  3. Backpressure in Node.js: The Problem Most APIs Ignore
  4. Why Streams Exist: Solving the Hidden Scaling Problem in Node.js

Start reading the first chapter:
Node.js Is Not Single-Threaded — And That Misconception Costs You Scale