System Design Interview Guide (2026)

System design interviews test your ability to build scalable, maintainable, and performant systems.

1. How to Design a URL Shortener?

A URL shortener like bit.ly can be built using hashing or base62 encoding to generate unique short codes. Store the mapping in a database and use caching (Redis) for fast retrieval. Load balancers distribute traffic across servers.

2. How to Scale Applications?

Scaling can be vertical (bigger machines) or horizontal (more instances). Use caching layers (Redis/Memcached), CDNs for static assets, and message queues (Kafka/RabbitMQ) to handle async tasks.

3. Microservices vs Monolith

Microservices allow independent deployment and scaling of components but increase complexity in communication and monitoring. Monoliths are easier to develop and debug but harder to scale for high traffic.

4. How to Design a Chat System?

Use WebSocket for real-time messaging, a scalable database (like MongoDB or Cassandra), and a queue system for message delivery. Ensure horizontal scaling for high concurrency.

5. How to Design an E-commerce System?

Break into microservices: product catalog, order service, payment gateway, and user service. Use caching for hot products and a CDN for images. Ensure ACID compliance for orders.

6. Load Balancing Techniques

Round-robin, least connections, and IP hash are common strategies. Load balancers distribute traffic and improve availability.

7. Caching Strategies

Use caching layers for frequently accessed data. Strategies include write-through, write-back, and cache-aside. Redis and Memcached are popular choices.

8. Database Scaling

Scale databases using vertical scaling, sharding, replication, and partitioning. NoSQL databases can help with massive scale.

9. Designing a High-Traffic API

Use rate limiting, caching, request batching, and async processing to handle millions of requests per day.

10. Event-Driven Architecture

Use message queues and event streams to decouple services. This improves scalability and maintainability for complex systems.

11. Monitoring & Logging

Use centralized logging (ELK Stack) and monitoring (Prometheus/Grafana) for observability, debugging, and alerting in production systems.

Practice these questions using our AI quick Preparation methods.