Just to put it on the record I am happy to acknowledge that duplication is an inconvenience as well as a security issue.
Your point about trusting conventional code is well made and important. Once I repeated that I shouldn't roll my own crypto. A cryptographer shrugged and told me, I mean, somebody has to write it, and that person might be you. (That person isn't me. I don't roll my own crypto. I do roll my own auth, because I'm comfortable with my understanding of authn/authz attacks. Use my software at your peril.)
Regarding complexity what I was thinking is that, after a lot of clever reflection, you might realize the proper solution is actually to take something away. To give an illustrative though not very realistic example, you might realize you didn't actually need a web backend at all and that the app can function local-only. Thereby solving your UX and security issues - client side validation is now completely acceptable. This architecture is simpler (less complex) in that the diagram contains fewer elements, but more sophisticated in that it contains more baked-in wisdom about how your normally web-based application can fulfill all it's requirements locally.
>To give an illustrative though not very realistic example, you might realize you didn't actually need a web backend at all and that the app can function local-only.
ssshhhh, don't give away the only secret that keeps us employed.
if they knew for certain our stuff wouldn't break, we wouldn't had been kept around.
Your point about trusting conventional code is well made and important. Once I repeated that I shouldn't roll my own crypto. A cryptographer shrugged and told me, I mean, somebody has to write it, and that person might be you. (That person isn't me. I don't roll my own crypto. I do roll my own auth, because I'm comfortable with my understanding of authn/authz attacks. Use my software at your peril.)
Regarding complexity what I was thinking is that, after a lot of clever reflection, you might realize the proper solution is actually to take something away. To give an illustrative though not very realistic example, you might realize you didn't actually need a web backend at all and that the app can function local-only. Thereby solving your UX and security issues - client side validation is now completely acceptable. This architecture is simpler (less complex) in that the diagram contains fewer elements, but more sophisticated in that it contains more baked-in wisdom about how your normally web-based application can fulfill all it's requirements locally.