That entirely depends on what these transactions are meant to do.

I always find these debate weird. How can you compare one app’s TPS with another?

Not if you’re going to be “web scale” (tm) you can’t.

You can host it on 8 raspberry pi's: Three for etcd, three for minio/ceph, and two for Kubernetes workers.

(16 if you need geo replication.)

You put one Mongo shard on each Pi, they are the secret ingredient in the web scale sauce.