Design Emergency Notification System
Company: Fora Travel
Role: Software Engineer
Category: System Design
Difficulty: medium
Interview Round: Onsite
Design a disaster or emergency notification system for an organization such as a city government, university, or large company.
The system should allow authorized operators to create urgent alerts and deliver them to affected recipients through multiple channels such as mobile push notification, SMS, email, voice call, and web banner. Alerts may target users by geography, organization group, subscription preference, or incident type.
Discuss the requirements, APIs, data model, high-level architecture, delivery workflow, scaling strategy, reliability guarantees, failure handling, security, and monitoring.
Overview: This question evaluates system design and engineering competencies related to large-scale, real-time notification systems, including distributed systems architecture, messaging and delivery mechanisms, data modeling, API design, scalability, reliability, security, and monitoring.
Community answers
Answer by alex.chin23
Functional Requirements:
Admin users can create,read,update notifications
Notifications can be pushed via Push Notifications, SMS, Email, Voice call, and Web Banner
recipients users can READ notifications
Non functional:
Highly Available 99.99%, over consistency. Incorrect or Stale notifications are ok.
Low latency, less than 500ms for initial notifications up to a minute
Scalable, notifications should be able to be fanned out to millions of recipients
Dedupe delivery layer
Entities:
Users
userId
email
name
location
organization group
subscription preferences
admin status: true/false
Notification
notificationId
description
severity
incident type
location
Delivery Attempt
notificationId
topic
provider
status
API Design
POST /incidents/
GET /incidents/{id}
PATCH /incidents/{id}
POST /incidents/{id}/publish
PUT /users/{id}/preferences
POST /recepients
POST /v1/notifications/{id}/ack → user acknowledged (stops escalation)
HLD:
Postgres for hosting incident metadata
Locations stored in DDB, TTL on device locations