Where the document database? There 3 cache implementation, and 2 of them with a data structure layer.
To be called a database you should actually have some acid compliance. Otherwise your just a datastore.
But this is a bit of bar banter on a public forum. which recently shown the ugly fact that senior software engineers does not read their reference documentation, but rather just use stackoverflow.
It is 2018 there is solid software(redis included) that can fulfill all 3 needs with one technology stack.
