Social Platforms, Chat & Real-Time Collaboration

Feeds, follows, comments, notifications, chat, media uploads and moderation for community products, plus live presence and collaborative editing for tools people use together.

Social features are easy to demo and hard to run. Each one needs data structures that scale with relationships rather than users, and each one can be abused. Feeds and ranking. A reverse-chronological query with keyset pagination goes a long way on PostgreSQL. As activity grows, I move to fan-out-on-write into per-user feed lists in Redis, with fan-out-on-read for accounts that have very large followings. Ranking starts with transparent signals — recency with time decay, relationship strength, engagement — that you can explain to users and tune. Notifications. In-app, email and push…