Index should fit in RAM or in cache?

[Prasad_Saya]

I think the RAM / memory refers to the total physical RAM available on the server (or specific node).

Also, see these articles:

• From the MongoDB blog Performance Best Practices: MongoDB Data Modeling and Memory Sizing see the section Memory Sizing: Ensure your working set fits in RAM

• Atlas Sizing and Tier Selection - Memory

• Discussion on this forum: Working set MUST fit in memory?