Server Development for App

Hello, I am building a mobile app that requires a back-end server to be developed. I have outlined everything that is needed for the back-end to be developed. The scope of the work shouldn't be very hard to do since it is a small-medium scale app. This will be a one time job that will be a hand off and will not require frequent updates since I will be hiring someone to do that job. What I need built: - Infrastructure - Back-end - Database - Notifications - Admin site Languages: - Redis (preferable for deleting expired post) - AWS (preferablably a storage unit that allows large post up to 25 mb) - other I don't mind what languages you use, so long as you are using cutting-edge technology. I want to ensure the back-end runs under stressful conditions if necessary and the ability to scale it horizontally (if need be; this is not a must) I need a way to make calls to the back-end (such as RESTful calls, etc.) to the front-end on my app on iOS and Android. I already have everything setup, but I just need a way to save user data. Please let me know if you have questions and I can explain anything in detail.