[half-kh-hacker]

the reference bluesky backend does just keep everything around but this idea has merit!! you're actually reinventing something like AppViewLite right now, which does throw away old data: https://github.com/alnkesq/AppViewLite

bluesky chooses to not refetch data from PDSes all the time so that the load for a PDS stays low (they like it to be possible to run on a home connection)