사용가능한 대역폭의 증가와 낮은 가격의 스토리지 → 어플리케이션에서 다루는 데이터의 증가 → How should they scale their db?
Sacling Up → expensive
Scaling Out → hard to administer
MongoDB is designed for Scaling Out
The topology of a MongoDB cluster, or whether there is in fact a cluster rather than a single node at the other end of a database connection, is transparent to the applica‐ tion. This allows developers to focus on programming the application, not scaling it.
Likewise, if the topology of an existing deployment needs to change in order to, for example, scale to support greater load, the application logic can remain the same.