How to work with private keys securely in bash?

Question

How to securely work with private keys in a bash script? My first attempt involves storing the encrypted key pair in a field in the database(mongo). However, I've since realised that I will have to use these keys in bash scripts, after being decrypted, in order to scp or ssh(key has to be a file so this will also increase IO).

This occurs inside an alpine linux container. Should I be concerned about using echo on a string containing a key?

I've also considered storing the keys in a container volume as files (id_rsa, id_rsa.pub) and referencing those paths in the database(or hardcoding a path). I am working with very many key pairs which go from DB to UI to API(3 separate containers) to BASH(in the API container)to create a connection and perform functions on each of these hosts. Which helps with the IO problem.

Is there a better way to do this? Should I be using some sort of keystore that I can store references for inside my DB?

In order of importance, Secure - Low IO - High Efficiency.