Hi, I have experience developing with both express and backbone js in production environments. We recently developed a similar app using both these technologies to provide simple public-key authentication to a shared keystore.
I propose 2 milestones (see below). As I try to follow the principles of TDD (test-driven development) whenever possible, I would propose writing test cases for the app first, and once you are happy that the test cases describe the required functionality, the changes will then be implemented.
TDD is a useful approach in this case, as it ensures that the specifications are agreed on before development begins.
Looking forward to hearing from you,
Phil