If I talk about working of horizontal sharding at blockchain for improvement of transactions processing then working is very simple which starts from creation of shard and further it moves to transactions routing and then parallel processing occurs and at last update related to states of shards are updated for continuing the consistency in network.

While STEEM don't use horizontal sharding in anyways for enhancement of transactions processing capacity and instead of it vertical scaling and witness based consensus are used by this blockchain which are also not bad options.

You did great job which is deserves to be appreciated.