encryption – Secure memory buffer

We are designing a Python application and we need to “load” encryption secret key in “memory” at the application boot.
It can be also an admin pin code. Anyway, just some data.

Our application will run under docker container.

What is the most secure process to do it ?
Can we trust the OS from any memory dump ?

Can we use some containers feature to isolate that part of memory to our process ?

Is there any kind of “secure/encrypted” cache system ? Redis ?

I believe that we MAY not find any extreme secure process, thus us there any obfuscation recommendations ?

Our application is targeted to run on the Cloud