I don't know if this will fit your needs, but couchdb is pretty fast. It's under active development and still alpha, so things do change. As for multi-key, it

I don't know if this will fit your needs, but couchdb is pretty fast. It's under active development and still alpha, so things do change. As for multi-key, it's a yes and no sort of situation. If you want to do an intersection you can, unfortunately it's in a sorted order. for example: [key1, key2, key3] won't match [key2,key1, key3] If you're trying just get all images matching a key so your structure looks like: {img (url, binaray, etc), tags: [tag1, tag2, tag3, tag4]} you can run a simple map function over the data function map (doc) { for each (var tag in tags) emit (tag, null); } which will allow you to then get all images by tag: key=tag It doesn't have a c++ api, but it uses http as its interface so you can use curl..