> What do you do regarding collections? (Dynamic arrays, hash maps)?

I don't do anything!

I use the most appropriate data-structure and minimal transformation necessary to get the work done. I use maths and higher-level tools to verify my designs but the implementation, when required to be soft-realtime needs to exploit as much mechanical sympathy from my target platform as possible.

You might be interested in https://dataorientedprogramming.wordpress.com

Cheers!