We run MongoDB mongod processes inside Docker containers in Kubernetes with clear memory limits.

I am trying to configure the mongod processes correctly for the imposed memory limits.

These are the information I could collect from the docs:

• The memory usage of MongoDB is correlated to the WiredTiger cache size. Its is calculated using the formula 50% of (RAM - 1 GB) or a minimum of 256 MB https://docs.mongodb.com/manual/core/wiredtiger/#memory-use
• RAM is the total amount of ram available on the system. In the case of containerized nodes, it is the available memory to the container (since MongoDB 4.0.9) https://docs.mongodb.com/manual/faq/diagnostics/#must-my-working-set-size-fit-ram
• “If you run mongod in a container (e.g. lxc, cgroups, Docker, etc.) that does not have access to all of the RAM available in a system, you must set storage.wiredTiger.engineConfig.cacheSizeGB to a value less than the amount of RAM available in the container.” https://docs.mongodb.com/manual/faq/diagnostics/#must-my-working-set-size-fit-ram
• The docs state that increasing the WiredTiger cache size above the default should be avoided. https://docs.mongodb.com/manual/faq/diagnostics/#must-my-working-set-size-fit-ram

This information is a little unclear.

Do I leave the default values of the WiredTiger cache size or do I set it to "a value less than the amount of RAM available in the container"? How much lower should that value be? (a higher value than the default would also contradict the advice to not increase it above the default value)