This is the last article for the moment. It is about things I don't know how to solve or have not yet had time to solve.
I've already mentioned this issue but I still don't know what is the root cause and how to mitigate it. The check to not insert already inserted transaction prevents creation of ~25 double transactions per day. Still, I see there is usually one double transaction per day (that is per ~2500 transactions). I am quite confident this is a sever side issue as __createdAt times are very close to each other.
POS does not work on iPhone
For some reason, the application does not work on iPhone. The main page is displayed, user is correctly redirected to the Google's sign in page but after successful sing in, she is redirected back to the main page which does not proceed to the next page. I've briefly tested the issue on borrowed iPhone and found out it is caused by combination of AWS and Durandal. Pure AWS page works just fine and I have not found any indicia that Durandal does not work on iPhone. I believe I just need to borrow the iPhone for longer time to fix this issue.
Built-in *.azurewebsites.net SSL certificate
The server is hosted on azurewebsites.net domain and uses built-in wildcard certificate for secure access. Although I have read several articles that using wildcard certificates is bad, I don't think it is bad in our case. It is a REST service where both endpoints are fixed. If you disagree, please let me know an example of real threat.
Authentication token expiration
The authentication token expires approximately every month. Which is the reason why I still have not developed automatic re-authentication when the token expires. It hasn't had enough priority.
There is a way how to do it generally for all requests by using withFilter (usage example). Or I will just sign out and in every couple of days. Whatever will be easier to implement.