MEAN Node.js Async Patterns and Performance 2

Question 1

What is the purpose of Node.js streams in a MEAN stack application?

Accepted Answer

Process data in chunks for memory efficiency, ideal for large file uploads or database exports

Answer

Stream real-time updates to Angular clients via WebSockets

Answer

Pipe data between MongoDB aggregation stages

Answer

Chain Express middleware functions together

Question 2

What does `async/await` syntax do in Node.js?

Accepted Answer

Makes asynchronous Promise-based code look synchronous, improving readability and error handling

Answer

Creates genuinely synchronous code that blocks execution

Answer

Converts callback-based functions to Promises automatically

Answer

Runs code on a background thread transparently

Question 3

What is the Node.js `EventEmitter` class used for?

Accepted Answer

Implements the observer pattern allowing objects to emit named events that listeners can respond to

Answer

Emits HTTP events from Express to Angular clients

Answer

Manages DOM events on the server side

Answer

Schedules recurring tasks in the event loop

Question 4

What is `util.promisify()` used for in Node.js?

Accepted Answer

Converts callback-style functions following the error-first pattern into Promise-returning functions

Answer

Validates that a function returns a Promise

Answer

Creates utility Promises for common async patterns

Answer

Adds timeout capability to existing Promises

Question 5

What is backpressure in Node.js streams and why does it matter?

Accepted Answer

When a writable stream can't consume data as fast as the readable produces it, and the readable should pause

Answer

When database writes create pressure on the event loop

Answer

When HTTP responses are too large for the TCP buffer

Answer

When too many concurrent requests queue up in Express

Question 6

What is the difference between `require()` and ES module `import` in Node.js?

Accepted Answer

require() is synchronous CommonJS; import is asynchronous ES modules with static analysis and tree-shaking support

Answer

require() is for npm packages; import is for local files only

Answer

require() loads at startup; import loads on demand always

Answer

Both are identical, import is just newer syntax