When to use a key-value data store vs. a more traditional relational DB?

Question

When would one choose a key-value data store over a relational DB? What considerations go into deciding one or the other? When is mix of both the best route? Please provide

Answer 1

If your data is simply a list of things and you can derive a unique identifier for each item, then a KVS is a good match. They are close implementations of the simple data structures we learned in freshman computer science and do not allow for complex relationships.

A simple test: can you represent your data and all of its relationships as a linked list or hash table? If yes, a KVS may work. If no, you need an RDB.

You still need to find a KVS that will work in your environment. Support for KVSes, even the major ones, is nowhere near what it is for, say, PostgreSQL and MySQL/MariaDB.