How does an index's document count affect performance?

Elastic Stack Elasticsearch
1

Are there any metrics, posts, or otherwise good information regarding how document size as well as the total document count on an index affects search performance? I understand other mitigating factors such as mapping, analyzer, etc., but how do the sheer numbers line up?

For example, I have a basic mapping with 5 general fields, no nesting, or anything special. How can I estimate search performance would be affected from say, 100k documents to 100 million or 1 Billion documents?

2

It can depend on a number of factors, so the best way to know is to benchmark using realistic data and queries on your hardware.