Experiences with ecto_instashard or Ecto sharding in general?

Just stumbled upon this library:

Any experiences or recommendations on the topic? I am looking for a reliable and easy to implement PostgreSQL sharding solution: a. At database level (not tables, but whole databases) b. managed at application level.

I think of distributing the data based on user groups, clearly distinguishable by group membership. Each group having its own databae instance.

Thank you.