Zentry
A cross-platform app for event management and QR access control — VIP, Standard and Staff tickets, a real-time scanner with sound and vibration, available on Android, iOS, Web and desktop.
The project
Organising an event in Malabo used to mean paper lists, photocopied tickets and manual access control. With Zentry, the organiser creates the event in minutes, adds guests from their phone and shares each guest’s QR code directly on WhatsApp — with a single tap.
At the door, staff scan the codes with the device’s camera. The system responds in under a second: valid ticket, already scanned, venue full or invalid code — each case with its own sound and vibration, so staff don’t need to look at the screen in a noisy environment. Duplicate entries are impossible.
The dashboard shows in real time how many people have entered, how many are still to come and how close the event is to capacity. Everything is synced instantly across all the team’s devices.
Zentry runs on Android, iOS, Web, Windows, macOS and Linux from a single app — which means the organiser manages from a laptop and the staff check tickets from their phones, without installing different apps.
Need something similar?
Tell us about your case: we start from what we have already built to get there faster and for less.
Related service: Mobile appsTechnical details
Challenges
- →Preventing two staff members from validating the same QR code at the same time — a race condition at the entrance
- →Instant feedback in noisy environments: the scanner has to communicate without relying on sound alone
- →Sharing individual QR codes on WhatsApp in high resolution from a phone
- →A single app that works on Android, iOS, Web and desktop without duplicating code
How we solved them
- A Supabase query with an atomic status update — if two devices scan the same QR code at once, only one gets through
- A combination of sound + vibration with distinct patterns for each result, falling back to vibration only
- Exporting the QR code as a high-resolution image (3x pixel ratio) before sharing
- Flutter, with platform-specific logic separated only where strictly necessary