I want to make a simple database for my backend server but I don't need something the size of mongo. I basically just want to track if the weather for a city has recently been sent to a client and cache it for a short time. I don't expect high traffic initially, and I may just store the json data in files and look at the timestamp, but would prefer an embedded database, since I will just have one server. I don't want to use H2 as I want the data saved. Kodein-DB states it shouldn't be used on the server. What else would work well?