Backend Interview Questions

calendarDec 14, 2025 · 2 min read · backend interview api databases microservices distributed-systems performance  ·
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Comprehensive backend interview questions covering APIs, databases, microservices, distributed systems, and performance optimization.

Overview

Backend development encompasses:

  • API Design: REST, GraphQL, gRPC
  • Databases: SQL, NoSQL, transactions, optimization
  • Microservices: Architecture, communication, scaling
  • Distributed Systems: Consensus, replication, sharding
  • Performance: Caching, connection pooling, rate limiting
  • Security: Authentication, authorization, encryption

Question Categories

Easy

  • REST API fundamentals
  • HTTP methods and status codes
  • Basic database operations (CRUD)
  • SQL vs NoSQL
  • Authentication basics (JWT, sessions)
  • Caching fundamentals
  • API versioning
  • Basic security practices

Medium

  • Microservices architecture
  • Database transactions and ACID
  • Message queues and async processing
  • Replication and sharding
  • Rate limiting strategies
  • Connection pooling
  • API gateway patterns
  • N+1 query problem
  • Index optimization

Hard

  • Distributed caching systems
  • Event sourcing and CQRS
  • Distributed locks (Redlock)
  • Saga pattern for distributed transactions
  • Real-time notification systems
  • Circuit breakers and resilience
  • Multi-tenant architectures
  • Job scheduling with priority queues
  • Distributed tracing and observability

Key Technologies

  • Languages: Node.js, Python, Go, Java
  • Databases: PostgreSQL, MySQL, MongoDB, Redis
  • Message Queues: RabbitMQ, Kafka, NATS
  • Caching: Redis, Memcached
  • API Protocols: REST, GraphQL, gRPC, WebSocket
  • Observability: OpenTelemetry, Jaeger, Prometheus

Interview Preparation Tips

  1. Understand Trade-offs: Every design decision has pros and cons
  2. Think at Scale: Consider performance with millions of users
  3. Know Your Tools: Deep understanding of databases, caches, queues
  4. Practice System Design: Design complex systems from scratch
  5. Code Quality: Write clean, maintainable, testable code
  6. Real-world Experience: Build projects, contribute to open source

Snippets