Bluesky's project name is 'Jetstream' and NATS.io persistence engine is `JetStream` (camel case), which can be confusing but name not exactly the same.

- NATS JetStream docs: https://docs.nats.io/nats-concepts/jetstream

- Bluesky's 'Introducing Jetstream': https://docs.bsky.app/blog/jetstream

The only ATproto-specific part is how clients specify their starting position. They give a timestamp, which refers specifically to the `time_us` field in the messages, which I guess must be an ATproto thing. If jetrelay supported filtering, that would be ATproto-specific too. But you’re right: if you removed backfill support there’d be nothing ATproto- or even websocket-specific about it.