Everyone have heard Node.js is fast. But fewer people know why or what specifically makes it a different beast compared to traditional server runtimes.
In Nodejs there are two important things to note down.
Here V8 (Chrome's JS engine) handles JavaScript execution. But the thing that makes Node.js fast for I/O isn't V8 it's libuv, a C library that powers the event loop, thread pool, and async I/O. When Node reads a file or makes a network call, libuv handles it at the OS level while your JS thread stays free.
What Nodejs offers
Blocking vs non-blocking I/O
Traditional servers handle one request per thread. While a thread waits for a database result, it just sits there blocked, doing nothing, burning memory. Node.js flips this instead of waiting, it registers a callback and moves on to the next request. When the data is ready, it circles back.
Event-driven architecture
Node.js is built around a simple idea: things happen, and you react to them. You don't sit and check "is the file read yet?" in a loop. You say "when the file is done, call this function" and walk away. That's the event-driven model.
Under the hood, the event loop runs in phases each responsible for a different kind of event. Timers fire in the timers phase. Completed I/O callbacks fire in the poll phase. setImmediate() runs in the check phase. Understanding this order stops a whole class of subtle bugs.
Single-threaded but not what you think
Single-threaded sounds like a weakness. It isn't. Node.js has one JS thread, but that thread is almost never the bottleneck if you understand JS properly or just follow my blogs.
Database queries, file reads, and HTTP calls don't run on your JS thread libuv offloads them to the OS or an internal thread pool. Your JS thread just dispatches work and handles results.
Concurrency vs parallelism
Parallelism is two cooks working simultaneously on two burners. Concurrency is one cook managing two pots starting one, monitoring both, stirring each when needed. Node.js is the one cook. Traditional multi-threaded servers are the two cooks. For I/O-heavy work, the one skilled cook wins less overhead, less coordination, less memory per request in flight.
When you genuinely need parallelism heavy encryption, image processing, ML inference use worker_threads. Unlike the cluster module (which spawns whole processes), Worker Threads share memory via SharedArrayBuffer. Your main thread stays free. Most devs still don't reach for it.
If you are building something on internet where to use Nodejs
Remember one thing no technology is the right for everything. Use it where it shines.
REST APIs and GraphQL servers
Real-time apps like chat, live feeds, collaboration
Streaming data pipelines
Avoid for CPU-heavy computation
Real Companies Betting on Node.js
Some of the highest-traffic systems in the world run on Node.js:
Netflix moved their frontend server layer to Node.js and cut startup time by over 70%. They serve over 200 million users. LinkedIn switched from Ruby on Rails to Node.js and went from running 30 servers down to 3 handling double the traffic.
Uber built their dispatch and notification systems on Node.js. The real-time nature of ride-hailing is a perfect fit for event-driven architecture.
PayPal found Node.js handled double the requests per second compared to their Java solution, with 35% lower response times.
Trello, Walmart, NASA, Medium all use Node.js in significant parts of their infrastructure. These aren't companies that chose Node.js because it was trendy.
Here's something that doesn't show up in benchmarks: Node.js shares JavaScript between your frontend and backend. Your team writes one language. You can share validation logic, type definitions, utility functions between client and server.
This isn't a Node.js performance feature. But it's a team performance feature. In organizations running at scale, the reduction in context-switching developers not needing to flip between Python/Java on the server and JavaScript on the client is genuinely significant.
I hope you get to know something valuable from the article.
I’m currently deep-diving into the JavaScript, building projects and exploring the internals of the web. If you're on a similar journey or just love talking about JavaScript, let’s stay in touch!
Keep coding and keep building.
