News Aggregator
Difficulty: Medium
What It Tests
Feed crawling, deduplication, topic clustering, feed ranking, and freshness.
Topics Covered
- Message Queues & Async Processing
- Database Design: SQL vs NoSQL
- Search & Elasticsearch
- API Design
- Fanout Patterns
- Web Crawling at Scale
- Database Indexing
Hello Interview Breakdown
Read the full Hello Interview breakdown →
Video Walkthroughs
Approach Hints
- Periodic crawl workers fetch RSS/Atom feeds from configured sources; deduplicate articles by URL hash and SimHash for near-duplicates
- Index articles in Elasticsearch for full-text search and topic clustering (ML-based category tagging)
- Rank feed by a combined score of recency + source trust + user engagement signals
- Personalize feeds based on user topic subscriptions; fan-out on read to blend personalized and trending content