What is the optimal number of records per shard?

Hello,

I am currently developing a PIR server using the pir-server-example repository.

We are anticipating a total of 10 million URLs for our dataset. In this context, what would be the optimal shard size (number of records per shard) to balance computational latency and communication overhead?

Any advice or best practices for handling a dataset of this scale would be greatly appreciated.

Thank you.