Why even have a "Terminology" or "Definition" tag if you can't even ask for "formal terminology" without it being considered "Opinion Based"?
Our community does not have a homogeneous opinion about what kind of terminology questions to keep and which to close. To my observation, specifically the three members who closed this questions are part of a subset who tend to close-vote each and every Terminology tagged question immediately, so they probably think those question are all too opinionated (others surely think differently about this). Don't expect to get an explanation from them, they seem to be pretty immune when their votings are questioned.
However, that does not mean those close votes were completely unjustified for this specific case. I have my doubts there is a "formal" terminology for the concept described in the question (assumed by "formal", we mean "a definition in some official standard"), so the correct literal answer to your question is most probably "no" - which does not make a particular interesting Q&A pair. If you would have asked for a "widely accepted term", you would probably have gotten the answer you got in the comments below your question ("key-value store"), still it is debatable and opinionated if this is a most-widely used term, or the primary term, or if other terms may be a better fit.
Currently, I don't see a good reason to vote for reopen this question - you got an answer in the comments, and in retrospection the answer sounds pretty trivial ("storage for key-values = key-value store"). If someone has surprisingly an idea about a better, not-so-trivial answer and wants to post it, they can leave a comment here and ask me for a reopen vote, then I will happily vote accordingly.