This is certainly not a complaint, but I am curious as to why Mongo 6 appears to consume in general far less memory than Mongo 4, with the same hardware, replica-configuration, same data, same indexes, same user activity, etc. I am no longer seeing large memory spikes that I used to see on Mongo 4 (sometimes resulting in swap usage), but the downside is that on a 64gb RAM machine, only about 20% appears to be used and remains consistently flat.
The only notable difference between my Mongo 4 setup and Mongo 6 is that I now have symbolic links of
local folders to a local SSD disk, separate from database data on a SAN.
Has there been some notable change between Mongo 4 and Mongo 5 that should see me allocate less resources to RAM and perhaps to CPU instead?