As with basically all software design questions, the answer is "it depends". Writing a LOB app with 4 expected users all located in the same location, and expe

As with basically all software design questions, the answer is "it depends". Writing a LOB app with 4 expected users all located in the same location, and expected storage requirements of a gigabyte a year? Go with a traditional DB, add replication if you need high availability, make and test your backups, done. Writing the new Facebook weknoweverything app that captures smartphone audio and video continuously for all users at all times, automatically transcribes all conversations and produces AI-driven summaries of all video, all of which are saved forever and highly searchable? You're going to need a highly customized data storage architecture to have a prayer of keeping up with that data. Somewhere in between? Some of those are good candidates for Spanner. Some aren't.