Design a price tracking platform
Overview
This question evaluates system design and distributed systems competencies, including scalable crawl/ingestion strategies, data parsing and normalization, product identity resolution, time-series storage and change-detection, and notification and API fanout architecture.
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Sep 6, 2025, 12:00 AM
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System Design: Price Tracking Platform for E-commerce
Context
Design a system that tracks prices across many e-commerce sites, builds historical price series, visualizes trends, and notifies users on price drops. Assume the platform must handle millions of products and operate under legal and robots.txt constraints.
Requirements
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High-level architecture covering:
- Crawl/scrape ingestion: schedulers, politeness, anti-bot handling, retries.
- Parsers and normalization: extracting price, currency, availability; standardizing units.
- Deduplication and product identity resolution across sites.
- Storage schema for price histories and current state.
- Change detection logic for meaningful price deltas.
- Alerting rules, user preferences, and notification fanout.
- APIs for search, product pages, price history, and subscriptions.
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Address non-functionals:
- Scale (millions of products/offers), freshness SLAs, failure recovery, per-domain rate limits, legal/robots compliance, and cost efficiency.
- Include technology choices for databases, queues, caching, and a backfill/replay strategy.
Assumptions
- “Product” is a canonical item (e.g., iPhone 14 128GB). “Offer” is a site/seller-specific listing for a product.
- Some sites expose structured data (JSON-LD/Schema.org), others require HTML parsing; a small fraction require JavaScript rendering.
- Users can follow offers or products and configure alert thresholds.
Solution
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