Node.js Is Slow? Only If You Don’t Know This 🚀

Source: Dev.to

Truth bomb

Node.js is not slow. Most Node.js applications are slow because developers use it the wrong way.

Common myths

• “Node.js can’t handle scale” ❌
• “Node.js is single‑threaded, so it’s slow” ❌
• “We should rewrite this in Java/Spring” ❌

Node.js powers Netflix, PayPal, Uber, LinkedIn, Walmart, and many more.

Why APIs feel slow

Blocking the event loop

// This blocks everything
const result = fs.readFileSync('big-file.txt');

// Non‑blocking version
fs.readFile('big-file.txt', (err, data) => {
  // handle data
});

Rule: Never use synchronous methods in production APIs.

Node.js characteristics

• Single‑threaded for JavaScript execution
• Multi‑threaded under the hood (libuv thread pool)
• Event‑driven & non‑blocking

Think of Node.js as a high‑speed express highway: if one truck stops in the middle (blocking code), everything jams.

CPU‑heavy tasks

Node.js is not ideal for:

• Image processing
• PDF generation
• Encryption loops
• Real‑time video processing
• Machine‑learning training

Offloading work

• Worker Threads for background jobs (BullMQ, RabbitMQ, Kafka)
• Microservices for heavy computation

const { Worker } = require('worker_threads');
// Use a worker to run CPU‑intensive code

Database bottlenecks

90 % of slow Node.js apps are actually slow databases:

• Missing indexes
• N+1 queries
• Fetching unnecessary columns

CREATE INDEX idx_user_email ON users(email);

Rule: Optimize the database first—Node.js is rarely the bottleneck.

Caching

If every request hits the database, the app will crawl. Use:

• Redis (in‑memory cache)
• HTTP caching headers

redis.get(key) || fetchFromDB();

Caching alone can improve performance by 10×–100×.

Parallel execution

await task1();
await task2(); // runs sequentially

await Promise.all([task1(), task2()]); // runs in parallel

Parallel execution matters.

Streams

Many developers ignore streams—a big mistake.

// Bad: loads whole file into memory
const data = fs.readFileSync('1GB.log');

// Good: low memory, high performance
fs.createReadStream('1GB.log').pipe(res);

Streams provide low memory usage and high throughput.

Horizontal scaling

Node.js scales horizontally, not vertically.

• Cluster mode
• PM2
• Kubernetes
• AWS Auto Scaling Groups

Run one Node process per CPU core.

When to avoid Node.js

Avoid Node.js for:

• Heavy CPU computation
• Real‑time video processing
• Machine‑learning training

Node.js shines for I/O‑heavy, high‑concurrency systems.

Recommended stack

• Node.js + Fastify / NestJS – handles millions of users efficiently.

Bottom line

Node.js is not slow. Bad architecture is slow. If you:

• Respect the event loop
• Optimize DB & caching
• Use async patterns correctly

Node.js will outperform most traditional stacks.

Read the original article on Medium