[jeffchao]

Probably the ecosystem and documentation. PaaS like Render, Fly, and even Heroku from back in the day offer addons/plugins/whatever that make the obvious choice out to be Postgres/MySQL. Then there's other tooling such as migration and various ORM adapters. Then there's a wealth of blogs, stack overflow q&a's, etc. And then Postgres/MySQL gets you quite far. Start with a single node -> scale the node -> add read replicas -> shard. Then, sharding becomes painful? Start looking at other data stores, remodeling your data, or eventing, etc.