You can use NestJs with microservice architecture.where you can also use socket.io for web socket. you can use MongoDB (For real-time data) & MySQL for customer management.if you don't want to implement websocket.you can use firebase.it gives realtime database & firestore.which can handle millions of connections and scale it up.

I would also go with NestJS. I would say Java is unnecessarily complicated and limited. And Python is not typed. TypeScript is powerful and typed and goes well with NestJS, especially using RxJS.

Django does not enforce backend-frontend separation, which probably was a good thing back in the days, but not anymore. But on the other hand enforces the project structure to you, which I don't like.

Just a simple Node.JS app with templating engine for UI can be sufficient for what you want to achieve.

Spring boot with Spring Security[JWT], Websocket, Thymeleaf or Mustache, and styling with Bootstrap.