Streams in Node.js are objects that allow you to read or write data continuously in chunks rather than reading or writing the entire data at once. A stream is an abstract interface for working with streaming data in Node.js. The node:stream module provides an API for implementing the stream interface. All streams are instances of EventEmitter. They are used for efficiently processing large amounts of data, making I/O operations more manageable.

What are streams?

Difficulty: 5/10

Readable/Writable streams, pipe and backpressure, transform streams

1
Streams in Node.js are objects that allow you to read or write data continuously in chunks rather than reading or writing the entire data at once.
2
A stream is an abstract interface for working with streaming data in Node.js.
3
The node:stream module provides an API for implementing the stream interface.
4
All streams are instances of EventEmitter.
5
They are used for efficiently processing large amounts of data, making I/O operations more manageable.

Scenario Questions

0-2 years experience

1How would you read a large CSV file line by line in Node without loading the whole file into memory?
2If you pipe a readable stream into a writable stream and the writable stream errors, what happens to the readable stream and how would you handle it?

2-5 years experience

1We need to implement a file upload endpoint that streams the incoming data directly to S3. What steps would you take, and what pitfalls might you encounter with backpressure?

Follow-up Questions

Can you walk me through how backpressure is signaled between a readable and writable stream?
What practical differences do you see between a duplex stream and a transform stream?
How does the pipe method handle errors by default, and how would you customize that behavior?