Jumped straight to the queue layer because that felt safe, but I underestimated how much they wanted to hear about the seat reservation problem specifically.
Start by clarifying requirements and scale (e.g., millions of concurrent users, peak events) and then propose a high-level architecture that separates concerns: read-heavy browsing vs. write-heavy purchasing. Focus on scalability, availability, and consistency trade-offs, and dive into critical components like inventory management, queueing, and database sharding.
Pro tip: Emphasize idempotency and exactly-once processing for payment and ticket allocation to prevent double-booking and duplicate charges, which are common pitfalls in high-concurrency systems.
Ask questions to understand expected read/write ratios, peak QPS, consistency needs, and budget constraints. Define functional and non-functional requirements.
Sketch a layered architecture with CDN, load balancers, stateless services, caching, and a message queue for asynchronous processing. Separate read and write paths.
Detail inventory management (e.g., using distributed locks or optimistic concurrency), database sharding, and caching strategies. Discuss how to handle hot keys and contention.
Explain auto-scaling, multi-region deployment, failover, and monitoring. Discuss trade-offs between consistency and availability (CAP theorem).
Recap the design, highlighting key decisions and their trade-offs. Mention potential bottlenecks and how to mitigate them.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.