Positives:
QR generation is working as expected.
Responsive UI
Critics:
phone number / business hours validation missing.
there is no “remove” option after clicking 'add" button.
Need to have a “progress bar” so that user will know QR code generation is in progress.
Bonus:
If you’re running the backend on your own standalone API, then use a load testing tool like jMeter
to analyze your application behavior when there’s a spike in demand.
Replicate 100k traffic with atleast 100 parallel users.
Also, analyze the I/O and CPU utilization during the same.
Because, QR apps are used by mobile users and they are very sensitive on memory/bandwidth usage of the application.