Event Check-in
An event entry app that keeps recording check-ins when the signal drops, without counting the same person twice.
Technical detail
Event entry has a specific problem: everyone arrives at once, and the signal at the gate is usually poor.
Each QR code scan, or typed code, becomes a command stored in the device's SQLite with an idempotency key. With a connection, it goes out immediately. If the response is lost on the way, the command waits for confirmation, and on the next sync the app asks the server about that same key. It only resends if the server says it never arrived.
Retries use exponential backoff with jitter, credentials live in the system's secure storage, and a demo mode runs without a backend. A k6 load scenario simulates the rush when the gates open.
Quality: TypeScript, ESLint, Vitest and Maestro, with CI on every pull request.