CertAIn Offline-First Check-In
An event check-in and credentialing system built to keep working when the venue network does not — NFC cards, QR codes and browser-local face recognition.
74.2
Mean SUS score
9
Study participants
3
Test scenarios
5
Blocked by one popup
What it does
- 📶 Offline-first by design
- 💳 Embossed PVC NFC cards
- 🔳 QR fallback
- 🙂 On-device face recognition
- 🔀 Local / cloud engine toggle
- 🗺️ Venue map
- 🎫 Event stamps
- 🧪 9-participant usability study
Built with
- Figma
- Node.js
- Azure App Service
- face-api.js
- NFC
- QR
The case study
Situation & Task
Event venues are exactly where connectivity fails — crowded halls, borrowed networks, no guarantee of signal at the door. A check-in system that needs the cloud to admit someone will fail at the worst possible moment. CertAIn was designed offline-first for that reason: NFC cards and QR codes for identification, and face recognition running in the browser rather than on a server.
Actions Taken
I produced the hi-fi prototype in Figma and ran the usability study — moderated think-aloud sessions with nine participants against a "tech-hesitant SME owner" persona, across three scenarios: NFC check-in, the venue map, and event stamps. I also handled the physical side, producing custom embossed PVC NFC cards with print-ready artwork — bleed, outlined text — through an overseas supplier.
Results Achieved
Mean SUS score of 74.2. The finding that mattered most was a failure: a map popup covering the route users needed, which blocked five of the nine participants. None of us had noticed it while building, because we already knew where the route was. Event Stamps was named the favourite feature unprompted by four participants.
What I took away
- Five of nine users blocked by a popup none of the builders could see is the clearest case for testing with strangers I have had.
- Designing offline-first changes the architecture, not just the error states — identification has to work with nothing behind it.
- A think-aloud protocol surfaces hesitation that a task-completion metric records as success.
- Print production has its own constraints — bleed, outlined text, supplier lead times — that a screen prototype never teaches you.