Subscription-based algo-trading mobile app

Subscription-based Algo-trading mobile app.
Tech Stack:
Flutter with Firebase(authentication)
The same code base for Android, IOS, and Web, and for all screens(mobile, tablet, laptop, etc..,)
Payment Gateway(Razorpay or PayU or anything else which can support multicurrency, net banking, Indian wallets, master, visa cards, e-Mandate, e-Nach, recurring billing payments)
AWS DyanamoDB NOSQL
The rest of the backend stack is hosted on AWS.
Please find the attached SVG in your browser for the application flow