Milan Jovanović • 8/15/2026

How Do You Build a Social Media Feed? (System Design)

This article explores the classic system design problem of building a social media feed. It starts with the naive fan-out on read approach, which queries and merges posts at read time, and explains its limitations at scale using Twitter's read-to-write ratio. It then introduces the single-writer rule for the write path and explains the fan-out on write strategy, where feeds are precomputed at write time. The article covers tradeoffs, including caching, TTLs, and when each approach is appropriate, providing practical guidance for engineers designing scalable feed systems.

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#social media #system design #Scalability