I will build the mobile application with flutter version 3. For backend, I will build the RESTful web services API with following specification:-
1) build in nodejs v+ or java springboot 4
2) API featured with openapi 3
3) API featured with oauth 2.0
4) API featured with swagger
5) API featured with graphQL
With these specification, I will build robust , scalable and secure RESTful web services API with documentation for web and mobile application in standalone or cloud server.