Mid-level (2-5 years)Node.js
What are streams in Node.js and why should you use them?
Quick answer
Streams process data piece by piece as it arrives instead of loading it all into memory, which lets you handle large files and network data efficiently; they come in Readable, Writable, Duplex and Transform types.
Reading a 2 GB file with fs.readFile loads all 2 GB into memory and can crash the process. A readable stream emits small chunks, so memory use stays flat. Streams can be chained: read, compress, then write.
Backpressure is the key concept: when the destination is slower than the source, the stream signals the source to pause. Use stream.pipeline() (or pipeline from stream/promises) instead of manual .pipe() chains, because it handles errors and cleans up all streams properly.
import { pipeline } from "node:stream/promises";
import { createReadStream, createWriteStream } from "node:fs";
import { createGzip } from "node:zlib";
await pipeline(
createReadStream("access.log"),
createGzip(),
createWriteStream("access.log.gz")
);