Did yall build all the database implementation components yourself, or are any of them open source / off the shelf? It sounds like Kafka could do the transaction log job, and overall the architecture sounds similar to XTDBv1 which does use Kafka for that component.
https://v1-docs.xtdb.com/concepts/what-is-xtdb/
I’m also curious if you support unique constraints on non-id columns, or if having writer actions close to the database kind of takes that role.