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

In my experience, if you're even asking the question whether to use traditional vs esoteric practices, then go traditional. While esoteric practices are sexy, challenging, and fun, 99.999% of applications call for a traditional approach.

With regards to relational vs KV, the question you should be asking is:

Why would I not want to use a relational model for this scenario: ...

Since you have not described the scenario, it's impossible for anyone to tell you why you shouldn't use it. The "catch all" reason for KV is scalability, which isn't a problem now. Do you know the rules of optimization?

1. Don't do it.
2. (for experts only) Don't do it now.

KV is a highly optimized solution to scalability that will most likely be completely unecessary for your application.