Speed

We rolled out a new architecture that makes the inbox feed 25x faster for the heaviest users (for whom the feed had gotten excruciatingly slow). It's now 3x faster for the median user and loads in <300ms for 99% users.

A bit more background for the technically curious…

We used to serve the inbox feed by querying it on the fly.

As we grew (now 3M+ subs), the query got slow. We also ran out of meaningful optimizations.

So, we switched to a fan-out model, where we incrementally pre-construct feeds as sources publish. More complex, but faster.