How do Streams improve performance compared to fs.readFile() for large files?
Updated May 4, 2026
Short answer
Streams improve performance over fs.readFile() for large files by processing data incrementally instead of loading the entire file into memory before any work begins. This reduces peak memory usage, enables backpressure-aware data flow, lowers latency by allowing processing to start immediately, and scales much better when handling multiple large files or concurrent requests.
Deep explanation
The fundamental difference is how data is loaded and processed.
fs.readFile()reads the entire file into memory and only invokes its callback (or resolves its Promise) after the full file has been read.fs.createReadStream()returns a readable stream that emits chunks of data as they become available, allowing consumers to process data continuously.
fs.readFile() behaviour
With fs.readFile():
const fs = require('fs/promises');
const data = await fs.readFile('large.log');console.log(data.length);The sequence is roughly:
1.…
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