What is the best way to optimize memory and swap in ubuntu server18.04?

Question

System administration

Problem: on test servers, there is a constant lack of memory, and the servers periodically stop responding, only a forced reboot helps.
At the same time, the memory shows that a little more than half is occupied, and the swap is at zero. We increased the swap by 2.5 times - the same thing, not so fast, but it also completely eats up the swap, while there is still enough memory.
I saw that it is recommended to set the value vm.swappiness=10, but there is a caveat that this is good for desktop Linux, and for servers the default value of -60 may be optimal. I would experiment myself, but I do not have root rights for this.
From your experience, which is better?

Answer 1

It is necessary not to "optimize memory", but to limit the processes in terms of the occupied volume.

Answer 2

And what does memory optimization have to do with it if it is not enough?
Look for processes that require a lot of memory, and limit their appetites.

Answer 3

Problem: on test servers, there is a constant lack of memory, and the servers periodically stop responding, only a forced reboot helps.
At the same time, the memory shows that a little more than half is occupied,

Then where is the confidence that the problem is in memory? Do you have CPU/IO monitoring?
What's in the logs?