Question: Design a system like Amazon.com.
Start by clarifying scope. Focus on: product catalog, search, cart, checkout, and order tracking.
Architecture: Microservices. Product Service (DynamoDB for flexible catalog), Search Service (Elasticsearch), Cart Service (Redis for fast reads), Order Service (RDS for transactional integrity), Payment Service, Notification Service (SQS + email/SMS).
Scale considerations: Millions of concurrent users during peak. Flash sales create x traffic spikes. Use CDN for static assets, auto-scaling for compute, and message queues to absorb checkout surges.
Discuss trade-offs: DynamoDB for catalog (flexible schema, fast reads) vs RDS for orders (ACID transactions for payments).