Efficient memory management is crucial for building scalable and reliable applications, especially when working with Node.js and NestJS. Poor resource management can lead to memory leaks, degraded performance, and even system crashes.

We'll explore best practices to avoid memory leaks and the tools you can use to monitor and optimize resource usage in NestJS applications.

📚 What is a Memory Leak?

A memory leak occurs when an application keeps references to objects that are no longer needed, preventing JavaScript’s garbage collector from freeing them. Over time, this leads to growing memory usage, performance degradation, and potential crashes.

🛠️ Best Practices to Manage Memory in NestJS

1. Avoid Circular References

When two or more objects refer to each other, circular references are created, making it harder for the garbage collector to clean them up.
✅ Use patterns like WeakMap for weak references when needed.

const wm = new WeakMap();
let obj = { name: 'Test' };
wm.set(obj, 'some value');
obj = null; // Now it can be garbage collected

2. Manually Release Resources

Always close database connections, sockets, and streams when they are no longer needed.

await this.databaseConnection.close();

In NestJS, use lifecycle hooks like OnModuleDestroy and OnApplicationShutdown to automatically release resources:

@Injectable()
export class AppService implements OnApplicationShutdown {
  async onApplicationShutdown(signal: string) {
    await this.databaseConnection.close();
  }
}

3. Properly Manage Event Listeners

Unremoved event listeners can cause memory leaks.

✅ Always removeListener or off listeners you no longer need:

this.eventEmitter.off('orderCreated', this.handleOrderCreated);

4. Control the Growth of Collections

Avoid storing unnecessary data in arrays or maps.
Clear them when they are no longer needed:

this.largeArray = [];

5. Use Streams for Large Files

When handling large files, use streams instead of loading the entire content into memory.

const stream = fs.createReadStream('bigfile.txt');
stream.pipe(process.stdout);

6. Monitor and Optimize Dependencies

Some third-party libraries can introduce memory leaks.
✅ Regularly review, audit, and update your project dependencies.

🔥 Tools to Detect and Prevent Memory Leaks

Node.js Inspector + Chrome DevTools

Start your app with --inspect to debug in Chrome:

node --inspect dist/main.js

From chrome://inspect, you can:

  • Take heap snapshots.
  • Monitor object growth.
  • Analyze memory usage.

Clinic.js

A powerful performance analysis suite:

npm install -g clinic
clinic doctor -- node dist/main.js

Generates visual reports about memory, CPU, and event loop behavior.

Heapdump

Capture memory snapshots (.heapsnapshot) for deeper analysis.

npm install heapdump
import * as heapdump from 'heapdump';
heapdump.writeSnapshot('/path/to/dump.heapsnapshot');

You can open these snapshots in Chrome DevTools to find memory leaks.

Memwatch-Next

Real-time memory leak detection:

npm install memwatch-next
import * as memwatch from 'memwatch-next';
memwatch.on('leak', (info) => {
  console.error('Leak detected:', info);
});

Prometheus + Grafana

For production-grade monitoring:

  • Use prom-client to expose memory metrics.
  • Visualize and set up alerts with Grafana. 
npm install prom-client
const client = require('prom-client');
const collectDefaultMetrics = client.collectDefaultMetrics;

collectDefaultMetrics();

const http = require('http');
const server = http.createServer((req, res) => {
  res.setHeader('Content-Type', client.register.contentType);
  res.end(client.register.metrics());
});

server.listen(8080);

🧹 Extra Best Practices for NestJS

  • Use DTOs and Pipes to validate and sanitize input data.
  • Apply clean architecture principles like CQRS or Hexagonal Architecture.
  • Properly manage Singleton instances.
  • Avoid heavy decorators or stateful interceptors unless necessary.

✨ Conclusion

Proper memory management in a NestJS application is not optional — it's essential for building stable and scalable services.
By following best practices and leveraging the right tools, you can detect and fix memory leaks before they escalate into major problems.

Remember: In production, a memory leak doesn't just hurt your app — it can hurt your business!