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How I Built a QR Ticketing System with Svelte and FastAPI
I built this system to support real event check-ins, not just demo traffic. That requirement changed how every architectural decision was made.
Architecture
The frontend handles operator interactions and scanner flow. FastAPI controls validation, ticket state, and secure check-in logic. Nginx terminates TLS and routes traffic.
Performance Priorities
- Fast first paint for scanner users on mobile devices
- Minimal round-trips on ticket verification
- Predictable behavior on weak event Wi-Fi
Operational Lessons
Shipping reliable software meant documenting edge cases and testing fallback behavior, not only writing feature code. The highest leverage was clear runbooks and validation safeguards.