A few ideas. The data model. How to map and continually re-map the server side model to the client side model. The design patterns appropriate to the problem

A few ideas. The data model. How to map and continually re-map the server side model to the client side model. The design patterns appropriate to the problem, for instance using redux middleware to implement an interceptor, and leveraging any number of message based programming patterns from the Patterns Of Enterprise Application Architecture book. The communication mechanism from client to server. The data serialization format. Establishing testing patterns that are reliable in preventing bugs and regressions.