Prerequisites

• I have written a descriptive issue title

Mongoose version

8.6.3

Node.js version

v18.20.4

MongoDB version

4.4.25

Operating system

Linux

Operating system version (i.e. 20.04, 11.3, 10)

No response

Issue

Description:

I am currently in the process of upgrading Mongoose from version 4 to version 8 in our project, and I've encountered a significant performance issue.

Summary:

• v4 performance: Acceptable speeds.
• v8 performance: Approximately 40% slower for findOne queries, despite find queries operating as expected (and even faster than before).

Details:

• Indexes and schema remain identical between v4 and v8.
• No special configurations or optimizations were applied during the upgrade.
• find queries exhibit improved performance under v8, but findOne queries are noticeably slower.
• same setting & same environment & same index

Steps to Reproduce:

• Run the same query using findOne on both Mongoose v4 and v8.
• Compare the query performance between the two versions.

Expected Behavior:

• Performance should be on par or improved in v8, compared to v4.

Actual Behavior:

• findOne queries are approximately 30% slower in v8 than in v4.