hi there! scylla is great :) we are built on the same framework seastar.io so we literally share code bases in that regard.

Main departure is we are only API compatible. It was an explicit choice to use Raft vs ISR and to not use ZK, etc.

but indeed, seastar is a really fun framework to build storage systems in. I know ceph is also doing a re-write of a subsystem in seastar for example.

I'm a fan of scylla too, but if I could go back in time I'd have recommended waiting until mid 2019 to migrate. 'Fully optimized C++ rewrite's tend to take years to become battle tested.

indeed. that's why we continuously _empirically_ prove that we are in fact safe - https://vectorized.io/validating-consistency/

there is no substitute to testing tho

there are 2 levels here. 1) raft has a proof (and a great phd dissertation from diego), but what matters is if we actually implemented it correctly. so 2) is we need to continuously test it. Denis did a lot of similar work at CosmosDB (microsoft) and has spent his career working on consensus.

Hopefully these eases some concerns.

In fact, we couldn't switch to Scylla prior to 2019 because their support of incremental counters wasn't yet complete.

totally. today if folks. need txns, they wouldn't be a good fit for us. What we found is about 90% of use cases are covered by the base api. For reference w/ all of the versioning there is something like 144 api calls you can make to kafka, most ppl use a small subset of those via high level clients. (java, python, librdkafka, etc)