does sharding affect querying speed

I am implementing horizontal scaling or my sql database. I am spreading my table onto multiple dataservers with sharding designs. I know that this technique is very good for handling large volumes of data, and/or big data analysis. Also if spread across with geographical design, could serve some users data faster on specific regions. Besides all these, does sharding increase query speed by much? Since indexes already come into place. What would be other horizontal scaling options than sharding, or tips on that ? To sum up my question: Imagine 2 identical table structures, one has 100 million rows, and the other has 1 million rows. They both have indexes set up, will 1 million one run queries faster than the other? Horizontal scaling help with that ? (Also more tips)