I experience problems with query performance in Mongoid.

The major part of time is taken by query plan but not query itself (the relation is 5-to-1) and this is not being changed after a number of requests.

https://www.mongodb.com/docs/manual/core/query-plans/

My expectations

DB should not spend that much time on analyze phase. Imo it never should be a bottleneck – no matter how bad my indexes are.

I expect mongo to adjust itself after several requests but it’s not.

Details

The query I am talking about is on big collection with big skip. Nevertheless I can see no reason why query plan works that strange: it seems like DB just not cache plan analyze results and perform it every request.

Environment:

• rails (7.0.8.1);
• mongo (2.15.1);
• mongoid (7.5.4).
• Mongo DB (same problems on 3.4.15 and 4.4.10)

Questions

1. Why it continues to take that much time on query plan in every request?

2. Does Mongoid have query plan cache functionality at all? If so:
   a) why am I experiencing such DB behaviour?
   b) does it have any API and where can I find any docs describing that? E.g. is there any way I can configure query cache plan in Mongoid anyhow (check query plan cache or clear it)?

Thank you in advance!