Backend Interview Questions

Backend interviews test your understanding of how systems work under the hood — from API design and authentication to caching strategies and database choices. These questions cover the core knowledge that backend engineers at every level need. Unlike algorithm questions that test problem-solving in isolation, backend questions test your ability to design, build, and operate real systems.

5 questions • 5 categories • Updated March 2026

API Design

Mid-Level 6 min

REST API Design — Best Practices for Interviews

What are the key principles of REST API design? How do you design a good API?

Security

Mid-Level 7 min

Authentication — JWT, OAuth 2.0, and Session-Based Auth Compared

Compare JWT authentication, session-based authentication, and OAuth 2.0. When would you use each?

Performance

Mid-Level 6 min

Caching Strategies — When and How to Cache in Backend Systems

What caching strategies do you know? How do you decide what to cache and when to invalidate?

Data Storage

Mid-Level 7 min

SQL vs NoSQL — How to Choose the Right Database

When would you choose SQL over NoSQL? What are the tradeoffs?

Architecture

Microservices vs Monolith — Architecture Decision Guide

When should you use microservices vs a monolith? What are the tradeoffs?