I've found the key value-based redis to be very easy to use, powerful and well-documented. Redis also seems to fit in well with the async nature of node.js apps

I've found the key value-based redis to be very easy to use, powerful and well-documented. Redis also seems to fit in well with the async nature of node.js apps. While it's mostly known as an in-memory store, redis also has a virtual-memory option which can be useful when you have a (relatively) small number of keys -all of which can fit into memory- that are associated with much larger values which cannot fit into memory. Sure, there is a swap cost, etc, but I found this to be quite acceptable for a small sync server app I'm building (after prototyping with MongoDB and SQLite).