Also, and I think I indicated this in the tech spec, the right way to do this (to allow overrides in the DB) is to look for the full hash, and if it doesn't exist, check if the prefix exists. This means we'll do two mongo requests (unless we do an `$or` query but we'll worry about that when performance is more important than getting more features out the door and if we figure out it's a bottleneck, which I strongly doubt) in the worst case, but that's fine. It will also allow us to redefine some of these redirections if ever that's necessary by simply creating the entry in the DB.