[xfitm3]

In my example of DB and backend: How could they be decoupled?

[eikenberry]

As far as runtime, applications and DBs are already decoupled. You have N application instances mapped to M database instances. Applications can usually scale pretty much with load. Databases vary wildly in how they scale and it depends on the DB type.

[analogj]

read only replicas, sharding, clustering, caching