I was in an environment where I only had SQL Server available, but I really wanted a key-value store, so what did I do:
Use SQL Server as a Key-Value store - Major Haxxors
In order to be a proper key-valuestore, one would need to add the ability to do searching etc, but as this was only a quick hack where I did not require the search, I did not implement it.
In case I would have implemented a search, I probably would have used something like Elastic Search.
While this approach is probably not advisable, it helped my to resolve my issue in a very short time. The biggest effort was in getting the upsert command correct. Do not hold me responsible if you use this in a production environment and it blows up on you!!