Back-End Development Back-End Performance and Caching 2

Question 1

What is a cache eviction policy and what does LRU stand for?

Accepted Answer

The strategy for removing cached items when the cache is full — Least Recently Used means removing the item accessed least recently

Answer

A backup rotation policy — Least Recently Used

Answer

A database archiving policy — Large Record Utility

Answer

A network routing algorithm — Load Redistribution Unit

Question 2

What is the thundering herd problem in caching?

Accepted Answer

A situation where many requests simultaneously hit the origin/database when a popular cached item expires

Answer

Many servers crashing simultaneously under high load

Answer

A network failure caused by too many connected clients

Answer

A memory leak caused by indefinitely growing cache size

Question 3

What is HTTP caching and which header controls cache duration for browser and CDN caching?

Accepted Answer

Browser and CDN caching of HTTP responses — controlled by the Cache-Control header

Answer

Server-side query caching — controlled by the X-Cache-Control header

Answer

Application-level memory caching — controlled by the Expires header only

Answer

Database result caching — controlled by the Pragma header

Question 4

What is the purpose of database query optimization techniques like selecting only needed columns?

Accepted Answer

To minimize the amount of data transferred from the database, reducing memory use and network overhead

Answer

To reduce the number of tables in the database

Answer

To prevent SQL injection attacks

Answer

To ensure queries use the correct data types

Question 5

What is async/await and why is it important for back-end I/O performance in Node.js?

Accepted Answer

Syntax sugar over Promises that allows non-blocking I/O operations, keeping the event loop free to handle other requests while waiting

Answer

A syntax for writing synchronous code in a more readable way without any performance benefit

Answer

A multi-threading mechanism for parallel CPU computation in Node.js

Answer

A framework for managing background worker processes

Question 6

What is memoization in the context of back-end performance?

Accepted Answer

An optimization technique that caches the results of expensive function calls and returns the cached result for the same inputs

Answer

Storing application logs in memory for faster retrieval

Answer

Loading application configuration into memory at startup

Answer

A technique for reducing memory usage by compressing data structures