I spent way too long on the review storage schema and barely had time left for the reward ledger, which is clearly the spiciest part of the problem.
Start by clarifying functional and non-functional requirements, then design the data model and API. Focus on the core challenges: vote toggling, efficient querying with sorting and pagination, and reliable bonus issuance. Discuss trade-offs and scalability.
Pro tip: Emphasize idempotency and exactly-once processing for bonus issuance to avoid duplicate payments, and consider using a ledger or transaction log for auditability.
Ask about scale, read/write patterns, consistency needs, and bonus rules. Confirm that only verified purchasers can review, and votes can be toggled.
Propose tables for reviews, votes, and bonuses. Include fields for user, item, review text, vote type, and timestamps. Consider using a composite key for votes to enforce one vote per user per review.
Define endpoints for posting reviews, voting, and fetching reviews with sorting (e.g., by date, helpfulness) and pagination. Discuss how to efficiently compute net up-votes and handle toggles.
Design a system to track net up-votes per reviewer and trigger a $10 bonus for every 1,000 net up-votes. Use a background job or event-driven approach with idempotency.
Discuss caching, sharding, and consistency trade-offs. Consider using a message queue for vote processing and bonus calculation to decouple components.
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