Musing similarly... Or just replace PostgreSQL's transaction log with Kafka, given all the Kafka's advantages. Seems to me that traditional RDBMSs cram too many seemingly independent subsystems into a single system, each one of which if separate and behind a well defined interface could be made substantially better. I think there's more room for software that is akin to SQLite - a library replacing RDBMS functionality within an application and thus allowing for composability on language-linking level as opposed to process-linking level (done with an orchestrator).