I'm curious what the later "shard-local" bits do, if anything? I have a very large cluster (256 shards) and I'm sending most of my data with a single "composite", e.g. 1234!<unique_id>, but I'm noticing the data is being split among many of the shards.
My guess right now is that since I'm only using the default 16 bits my data is being split across multiple shards (because of my high # of shards). Thanks, Brett