Price Tracking Service Design

Specify the core service contracts and identity model for product resolution, canonical products, merchant listings, watchlists, current-price reads, and paginated price-history reads.

Design a persistence architecture for products, listings, price observations, watches, and alert state, justifying datastore choices, indexes, partition keys, retention policies, caching boundaries, and consistency semantics from the access patterns.

Select and justify a price-acquisition strategy across merchant APIs, product feeds, and web crawling using coverage, freshness, cost, reliability, rate-limit, and compliance constraints.

Design a horizontally scalable price-check scheduler with distributed work ownership, per-source rate limits, adaptive priorities, jitter, retry policies, and backpressure.

Design an asynchronous ingestion path that validates price observations and updates current-price and historical state correctly under duplicate, delayed, and out-of-order events.

Design a threshold-crossing state machine and notification workflow that provides effectively-once user-visible alerts over at-least-once infrastructure through durable state, idempotency keys, retries, and re-arming rules.

Conduct a failure-mode analysis of collection, ingestion, storage, alerting, and third-party dependencies, mapping critical failures and overload conditions to monitoring signals, graceful degradation, and recovery mechanisms.

Deliver a time-boxed end-to-end system-design walkthrough that connects requirements and estimates to component choices and defends bottlenecks, trade-offs, failure handling, and scaling evolution under interviewer follow-up questions.