> As has BlueSky, as long as you had enough hardware to keep up with the firehose

We've already explained to you twice that this is incorrect, you don't need to do this. And that if you do want to do this for some ridiculous reason, just because, a $5 VPS can do it.

But you do acknowledge latter you are only talking about tangled records.

Currently very few people are worried about this problem, because all of the tangled traffic just isn't that big, and you can drop most of it very quickly with little impact. Relays do allow various kinds of filters though. You could use a service like Microcosm Constellation https://constellation.microcosm.blue/ that lets you find only records for your repos etc. That would work fine for finding the records pertinent to you!

No one does this right now, because the premise is faulty. There just really isn't any difficulty or cost of any note to having all the tangled records piped at you. Hopefully some day this gets worse, and that this becomes a good problem to have! One we already have tools (like constellation) to tackle.

In short: constellation is a (also easy to self host cheap light weight) service for reverse indexing, for finding records pertinent to you. Lots and lots of atproto apps use this for this kind of "find people making records about my stuff".