Structured transactions between applications is one place. You can get by with files, but they're slower. A DB is the right choice. Structured data anytime yo

Structured transactions between applications is one place. You can get by with files, but they're slower. A DB is the right choice. Structured data anytime you're hitting multiuser - web, networked games, collab programs, live maps, etc. Anything that's massively stateful. A DB hands you a lot of guarantees. The filesystem has some of them, but is much slower.