Consider migrating to tiedot

[darenliang]

Nikel's data is served from memory, a persistent database might be better (memory usage wise) however a remote MongoDB instance might incur too much latency and might be overkill.

It might be good to migrate the in-mem store to an embedded persistent NoSQL database like tiedot. I suspect it'll be noticeably slower since there isn't a good way to index some search operations.