Question 1

What are the four types of streams in Node.js and what is the function of each?

Accepted Answer

The types are: readable (for reading), writable (for writing), duplex (for both independently), and transform (for modifying data as it passes through).

Question 2

What is the backpressure phenomenon in Node.js streams and how is it handled in engineering terms?

Accepted Answer

It occurs when the readable produces data at a rate faster than the writable can consume it, and is handled by pausing reading temporarily when the buffer is full and resuming it on the drain event.

Question 3

Why is it always recommended to use stream.pipeline instead of traditional chaining through .pipe()?

Accepted Answer

Because pipeline manages error handling and automatically closes and destroys all connected streams if any error occurs, while .pipe() leaves the streams hanging.

Question 4

What is the Buffer object in Node.js and how does Buffer.alloc allocation differ from Buffer.allocUnsafe?

Accepted Answer

Buffer is a raw binary memory region; Buffer.alloc zero-fills the memory to guarantee safety, while allocUnsafe reserves non-zeroed space faster but with the risk of exposing old data.

Question 5

What is the role of the highWaterMark option in streams and how does it affect memory efficiency and performance?

Accepted Answer

It specifies the maximum size of data stored in the internal buffer before backpressure is triggered and reading is paused.

Question 6

How do you design large file uploads as streams in an HTTP server without storing the file in memory?

Accepted Answer

Pipe the HTTP request stream (req) directly through a pipeline to a disk file or cloud storage (S3) as a multipart stream as its chunks arrive.

Question 7

How do you create and customize a Transform Stream to process data as it flows through Node.js?

Accepted Answer

Extend the Transform class and implement _transform(chunk, encoding, callback) to modify the data and pass it to the next stage through this.push(data).

Question 8

When should you use fs.readFile, and when should you prefer fs.createReadStream for working with files?

Accepted Answer

Use fs.readFile for small, fixed-size files such as configuration files, and fs.createReadStream for large files or continuous streams to conserve memory.

Question 9

What is Object Mode in Node.js Streams, and when should it be enabled?

Accepted Answer

It allows a Stream to pass and receive JavaScript objects and values instead of only bytes and Buffers.

Question 10

How do you close Streams manually with .destroy(), and why is it important to handle error events?

Accepted Answer

Calling .destroy([error]) closes handles and releases resources immediately to prevent network sockets or open files from leaking.