Terms Aggregation - Maximum acceptable cardinality

Elastic Stack Elasticsearch
1

I have an id field (keyword field) with one billion unique values. What will be performance impact of terms aggregation on this field with a size parameter of 10000.

2

The composite aggregation is a better approach (version >=6.1) :

https://www.elastic.co/guide/en/elasticsearch/reference/6.5/search-aggregations-bucket-composite-aggregation.html