I have to filter users that already interacted with each other, so they don't appear in search anymore.
I'm planning to do this filtering using a has_child query. The main user document will be the parent, and a child document will be created for each interaction.
I'm a bit concerned about these points:
Sparse data: The child documents will have just a few fields compared to the parent ones. I will deactivate doc_values for the fields I'm not pretending to sort and aggregate with, but still.
Number of documents will larger in shards with heavy users: Parent document and all of its children must live on the same shard.
Performance of the