Validating email is simple, right? Just throw a regex at it? Well it’s not as simple as you might think. The RFC Spec (Page 27 of this monster, if you’re interested) is clear as mud on what constitutes a valid email.
So you figured out Where Flux Went Wrong and are shipping your app with Redux. How will you measure usage? Will you know how users are using it once it’s launched? What about user authentication? You’ll definitely want to track that. But how will you do it?
Data is what programming is all about. Applications would be nothing without that beautiful i/o of data moving between modules, services, and data storage. But data is nothing if it’s not consistent.
Flow is pretty awesome.
In your web application, how secure do you require your users’ credentials to be? Do you require passwords to be a certain length, with enough kinds of different characters? Maybe you’re more progressive and employ two-factor auth, or alternative auth like biometrics or single-use SMS keys. If you do use passwords, maybe you’re using a compute or space-expensive hashing algorithm like bcrypt, scrypt, PBKDF2, or Argon2 to keep them safe. Maybe you’re encrypting your entire database on disk to keep your users as safe as possible. Nothing short of an attacker compromising your live database could leak that data out.