Jetstream (Bluesky)
A lightweight, JSON-based version of Bluesky's firehose. The raw firehose is binary (CBOR/CAR) and heavy; Jetstream delivers the same events as plain JSON over WebSocket, with the ability to filter by collection type — much easier to build against.
The problem it solves: the full atproto firehose requires handling CBOR decoding, Merkle-tree verification, and high data volume → a high barrier for hobby developers. Jetstream sits in front, decodes, and serves plain JSON, and lets you subscribe to only, say, posts or only likes. Trade-off: you lose the cryptographic verifiability (you trust the Jetstream server) in exchange for simplicity and lower bandwidth. Use case: quickly building a bot, a dashboard, or a simple custom feed without heavy infrastructure. Run by Bluesky but open source → you can host your own. It dramatically lowered the barrier to experimenting with the network's data.