Design a 911 emergency calling service

Q: Design a 911 emergency calling service

This question evaluates a candidate's ability to design a highly available, scalable emergency-calling platform covering real-time call flow, accurate caller location validation, PSAP routing, interoperability with telephony/SIP providers, and regulatory/security considerations.

Q: How do I approach System Design interview questions?

System Design questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master system design interviews.

Question

System Design Prompt

Design a 911 emergency calling service (or emergency call routing platform) that allows users to place emergency calls from mobile/landline/VoIP devices and routes them to the correct emergency response center.

What to cover

End-to-end call flow (caller → network → emergency service → dispatcher)
How you determine and validate caller location
How you route to the correct PSAP/dispatch center
Reliability and availability targets (e.g., "five nines")
Handling spikes (regional disasters), partial outages, and degraded modes
Data retention, audit, security, and compliance
Observability and operational runbooks

Assumptions

You can focus on the backend/platform design and interop boundaries (telephony providers, SIP gateways, PSAP interfaces), not the physical radio systems for first responders.

Design a 911 emergency calling service

Quick Overview

System Design Prompt

What to cover

Assumptions

Solution

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