I more or less built my own database in Erlang a few months ago. I say "more or less" because I did use Bitcask as the underlying store, and I used the riak_core libraries initially, but I did handle replication and different fault tolerance techniques on my own.
It was actually very fun; a key-value database is something that can be any level of difficulty that you want. If you want a simple KV "database", you could just serialize and deserialize a JSON string all the time, or write a protobuf, but there is of course no limit to the level of complexity.
I use the JSON example because that was actually how I started; I was constantly serializing and deserializing JSON with base64 binary encoded strings, just because it was easy and good enough, and over the course of building the project I ended up making a proper replicated database. I even had a very basic "query language" to handle some basic searches.
Any repo? even if not production ready. I'm curious about how you approached replication, compared to mnesia or couchdb, especially now that erlang natively supports json.
That's not a high bar to clear. Who's realistically going to use a laptop/desktop with a Core 2 Duo (2006), for instance?