Design an online auction system
Company: Meta
Role: Software Engineer
Category: System Design
Difficulty: easy
Interview Round: Onsite
Design a scalable online auction service.
Users can:
- Create an auction (item info, start/end time, reserve price optional).
- Place bids while the auction is live.
- See the current winning bid and bid history.
- Receive near-real-time notifications when the winning bid changes and when the auction ends.
Design goals and constraints:
- Many auctions run concurrently; bids can spike near the end.
- Correctness: determine the winner unambiguously; prevent accepting bids after the end time.
- Low latency for bid placement and for notifying watchers.
- The system should scale horizontally.
What APIs, data model, storage, messaging/pub-sub, and real-time push mechanism would you use? Include a rough QPS/throughput estimation approach and how you would partition/shard data (e.g., by auctionId).
Quick Answer: This question evaluates system design skills—scalable distributed architecture, real-time messaging and push, concurrency and consistency under contention, API and data-model design, throughput estimation, and partitioning strategies—and is categorized under System Design.