Ok right I see your point on making it easier for "common" cases. Still that forces to code defensively: if you're using this API it is likely you don't know yet the sharding setup, or at least didn't hardcode it. In other words, the caller would need to invoke both methods anyway and deal with both possibilities.

If we want to stick with the current approach then I think we should find a more suitable name as this is representing multiple indexes and is not a good home for other index-specific elements (in case we want to expose them).