I personally like to find new distributed systems, and then learn what techniques they use.

For example learning how serf.io ises Vivaldi, how CockroachDB uses raft multi-group, or why FoundationDB has different processes and they each do.

I try to write interesting stuff on distributed systems, but there's a great discord created by eaton phil on software internals that has a lot of great discussions https://twitter.com/eatonphil