Thanks for the discussions. I do anticipate that Accord will make things very much better, however I think if consumers are ultimately going to be replay the log into some other system (say Apache Iceberg) exact-once delivery will always be tricky, but perhaps not entirely necessary given the linearizability guarantees Accord will bring, either to safely replay mutations in order or to do something like "APPLY mutation IFF current.txn_id < mutation.txn_id". This does still mean some load on the end user to verify, even if the guarantees are stronger, and not too far off what we currently recommend to verify the last-write-win timestamps. (My Accord insight is obviously limited so I'm happy to be corrected if I'm wrong anywhere here!)
On token leadership, the Sidecar comes with soft/implicit primary range ownership of the co-located Cassandra node(s), we implemented a basic failover process to satisfy availability upto RF=3, but I think for strong guarantees hooking into TCM would be the ultimate goal. James.
