Blacksky has released its fork of the AT Protocol reference implementation, bluesky-social/atproto, with significant performance optimizations and community-focused features. The fork, available on GitHub as blacksky-algorithms/atproto, powers Blacksky's AppView at api.blacksky.community and is published for transparency and community benefit.

Key improvements include replacing the built-in TypeScript firehose consumer with rsky-wintermute, a Rust-based indexer that processes 10,000+ records per second versus the original's 90 records per second. This architectural change reduces a full network backfill from 6.5 years to a manageable timeframe. The team also implemented PostgreSQL LATERAL JOIN optimizations for timeline queries and added a Redis caching layer for actor profiles, records, and interaction counts.

Additional enhancements include server-side notification preference enforcement, JSON sanitization to prevent parsing errors from null bytes and control characters, and fixes for auth verifier stale signing key issues. The fork also introduces infrastructure for private community posts with separate membership gating and a custom lexicon namespace. While the repository isn't accepting contributions, the optimizations demonstrate how scaling AT Protocol implementations requires rethinking core components like the firehose consumer and database query patterns.