Mobile App for Electronic Queues: Eliminate Waiting Chaos
When a visitor steps away from the queue and misses their call, the entire system stalls. Operators waste time reassigning tickets, and throughput drops. A mobile app with real-time synchronization solves this: tickets update instantly via WebSocket, and personalized push notifications alert users when they are 3, 2, or 1 position away. In one of our projects for a regional MFC with 15 windows and 2,000 daily visitors, idle time dropped by 40% (from 8 minutes to 4.8 minutes per visitor), and operator time spent on re-assignments fell by 20%.
Technical Challenges We Solve
WebSocket vs SSE vs Polling
The core challenge is keeping the queue state in sync without overwhelming the server. We use WebSocket for bidirectional, low-latency communication. With a persistent connection, the server pushes events as soon as a number is called. On Flutter, we use web_socket_channel and manage state via Riverpod StreamProvider or BLoC. WebSocket delivers updates in under 100 ms — three times faster than SSE and orders of magnitude faster than polling.
| Approach | Speed | Complexity | Latency |
|---|---|---|---|
| WebSocket | High | Medium | 50–100 ms |
| SSE | Medium | Low | 200–300 ms |
| Polling | Low | Very low | 5–10 sec |
Background App and Push Notifications
When the app goes to background, the WebSocket closes. To avoid missed calls, we implement a two-tier notification system:
- "3 people ahead of you" — forewarning.
- "Your number is next!" — time to approach.
- "You are being called to window 5" — immediate action.
Push notification setup details
For iOS we use APNs, for Android — FCM. Correct certificate setup in App Store Connect and Firebase Console is critical. Push notifications must comply with App Store Review Guidelines Section 5.1. Code signing and provisioning profiles add an extra layer of security.
Pre-booking and Reminders
Advanced scenario: users book a specific time slot. The server (using Bull Queue on Redis) schedules push reminders 30 minutes and 10 minutes before the slot. This reduces no-shows by 35%, as seen in our medical center deployments.
Our Approach: Building a Reliable Queue System
Stack and Architecture
- Backend: Node.js + PostgreSQL + Redis + Bull Queue
- Mobile: Flutter (or React Native) with single codebase for iOS and Android
- Push: FCM + APNs with personalized targeting
- CI/CD: Fastlane + Shorebird for over-the-air updates
Case Study: MFC Deployment
A large MFC with 20 windows and 3,000 daily visitors needed to reduce chaos. We built a Flutter app with WebSocket sync and push notifications. Key metrics after launch:
- Average wait time per visitor: from 12 minutes to 7 minutes (41% reduction)
- Missed calls: from 18% to 4% (78% reduction)
- Operator overhead: cut by 22% due to automated call management
The system handled 5,000 concurrent WebSocket connections without degradation.
How We Work: From Discovery to Launch
- Analysis: Study visitor flow, number of windows, service types, user scenarios.
- Design: Architecture for queue management (in-memory Redis queue), API schemas, UI mockups.
- Implementation: Backend on Node.js + PostgreSQL, mobile on Flutter, push notification setup.
- Testing: Load testing up to 1,000 concurrent users; usability testing.
- Deployment: CI/CD pipeline, app store submission, monitoring (Crashlytics).
Contact us to discuss your project and get a preliminary estimate.
Timeline Estimates
| Scope | Duration |
|---|---|
| MVP: ticket, position, push notifications | 4–6 weeks |
| + Pre-booking, operator panel | 8–10 weeks |
| + Analytics, multi-office support, integrations | 14–16 weeks |
Common Mistakes to Avoid
- Ignoring background state: Without push fallback, users miss calls. Our system ensures WebSocket and push work in tandem.
- Using polling under high load: Polling at 5-second intervals on 5,000 clients generates 1,000 requests/second. We use WebSocket to reduce server load by 90%.
- Not testing with realistic concurrency: We simulate peak loads to guarantee stability.
What's Included in the Development?
- Mobile app (iOS + Android) and backend service
- Integration with existing systems (e.g., MFC management software)
- Push notification setup (FCM + APNs)
- QR code generation and scanning for tickets
- Admin analytics dashboard (visitor count, average time, peak loads)
- API and architecture documentation
- Staff training on admin panel
- 3 months of post-launch support