Oh I see. I think what you were looking for is the [sadd](http://redis.io/commands/sadd) command — `set` is for string values, not actual sets. The only problem with using a set is that it would generate hashes based on the entire JSON string, which is totally overkill. I think `hset` is the right one to use here, because it'll hash based on the ID instead.

/cc @cvan