Author here.
Thanks for sharing! My choices are pretty coloured by personal experience, and I didn't want to re-tread anything from the book (Redis/Valkey, Neo4j etc) other than Postgres - mostly due to Postgres changing _a lot_ over the years.
I had considered an OSS Dynamo-like (Cassandra, ScyllaDB, kinda), or a Calvin-like (FaunaDB), but went with FoundationDB instead because to me, that was much more interesting.
After a decade of running DBaaS at massive scale, I'm also pretty biased towards easy-to-run.