To use backend workflows or not?

I know there’s a lot of discussions going on about the new WU charges and structure and this is making me think if I need to reconsider how I am building my platform.

So what I am building needs to be highly secure as it will have personal details on it but also sensitive information for large companies, possibly some government sites.

My intention was to move as much of my workflows to the back end so they are server side to help with security. However I believe with the new structure this is now likely to cost me a lot more?!

This is a topic for advice on should I change it all to backend workflows but also to discuss how to make the app super secure too so any thoughts and recommendations would be useful.