So you’re a developer. Beautiful. That makes it easy then.
Look, you mentioned Postgres. But why use it at all for anything? Because redoing all the features that separate product provides is a giant pain in the ass. Now, what if your needs didn’t quite work with trad-relational DBs? Too much data, reads a million times higher than writes, no need for real-time accuracy. Then you use a specialized db like BigTable.
There are other services you plug into instead of reinvent. You stand up web servers with special features like redirect rules as configuration. You could write your own web service every time you start a new app, but that’s crazy. The need Apache or whatever is filling is a communications management piece.
Ok. Now. You are building a service and you need to build a transaction system for trading of digital assets with fiat currency. You could write your own or you could use a specialized service. NFTs on crypto currency are that prebuilt service. I’m switching metaphors now, but it’s just like picking a Docker provider.
Yes. Finder is just some app you can move files with on macOS.