Explain Geofencing Architectures.

Geofencing architectures define how systems detect when a device enters or exits a virtual geographic boundary and trigger actions via client-side, server-side, or hybrid processing.

When to Use

• Proximity marketing (store coupons on arrival)
• Logistics and fleet tracking
• Ride-hailing (driver arrival alerts)
• Safety alerts (restricted zones, emergency)
• Compliance (drones, healthcare monitoring)

Example

A delivery app can send a push notification when the driver is within 200m of the customer while updating ETA in the backend.

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Why Is It Important

Efficient geofencing architectures minimize false alerts, save battery, and maintain privacy. They also ensure accurate event logging for compliance and business intelligence.

Interview Tips

• Clearly outline client-side vs server-side vs hybrid models.
• Discuss trade-offs in latency, accuracy, cost, and privacy.
• Sketch data flow: Device → API Gateway → Rules Engine → Event Bus → Consumers.
• Highlight scalability (millions of devices reporting simultaneously).

Trade-offs

• Client-side: Fast and offline-capable, but higher spoofing risk.
• Server-side: Centralized control, but increased latency and cost.
• Hybrid: Balanced, but adds complexity.

Pitfalls

• Over-polling location (battery drain).
• Assuming circular fences (venues often need polygons).
• Ignoring offline buffering.
• Not handling privacy consent and data minimization.