Design a GitHub-like user community

System design: GitHub-like user community

Design the backend for a “developer community” product inspired by GitHub’s social layer.

Core requirements

• Users can sign up/login and manage a profile.
• Users can follow/unfollow other users.
• Users can create posts (text + optional links), and other users can comment and like .
• Each user has a home feed showing recent posts from people they follow (reverse-chronological is fine).
• Basic notifications : someone followed you / commented on your post.

Non-functional requirements

• High read volume (feed reads dominate). Assume a large-scale system; discuss how you would handle high TPS.
• Low latency for feed reads (p95 target you choose).
• Reasonable consistency (define what must be strongly consistent vs eventually consistent).
• Prevent obvious abuse (rate limiting / spam), at least at a high level.

What to deliver

• APIs (high-level request/response shapes are enough).
• Data model (tables/collections, key indexes).
• Architecture (services, storage, cache, queues/streams).
• Feed generation approach (fan-out on write vs fan-out on read), and trade-offs.
• Scaling and reliability (sharding/partitioning, replication, backpressure, failure modes).