Awesome question! We'd experimented with
https://github.com/lni/dragonboat and the hashicorp/raft in the early implementation, the etcd/raft library had been ported to a multi-raft style implementation by CockroachDB way back when, but they went the way of TigerBeetle and coupled their consensus deeply with the kv storage. Etcd has recently in v3.6 abstracted out their raft implementation and gave a pluggable interface into the transport layer, which meant that we could implement our own multi-raft style transport layer with heartbeat and multi-node message buffering on top of HTTP/Quic.
We implemented chaos testing suites akin to Jepsen to cover as many scenarios as possible and are currently implementing TigerBeetle style simulation tests on top of that for harder to reproduce scenarios!