Design an incident monitoring and alerting service similar to PagerDuty

Design a monitoring and alerting service similar to PagerDuty that can be used to handle production incidents in real-time. The system should receive alerts from external systems, identify the severity of incidents, and notify on-call engineers through their preferred channels (e.g., SMS, email, or push notifications). The system should also support configurable on-call schedules with both primary and secondary engineers assigned to incidents. Additionally, the system must have an escalation mechanism to ensure incidents are addressed based on their priority. Describe how you would design the system to scale effectively and maintain reliability during peak loads.

Designing a monitoring and alerting service, similar to PagerDuty, requires a reliable, scalable architecture that ensures incidents are detected, analyzed, and responded to in real time. At the core of the system, a monitoring service would gather metrics from various applications, databases, and servers. These metrics (such as CPU usage, error rates, and request latencies) would be stored and analyzed to detect anomalies or threshold breaches that trigger alerts. To handle high volumes of incoming data and ensure low-latency processing, a message queue such as Kafka can be used to buffer and distribute the metrics to analysis services.

The system would also require a persistent database like PostgreSQL to store configurations, on-call schedules, and incident logs. Redis could be employed for caching frequently accessed data, such as current on-call schedules and notification preferences, to ensure fast lookups. The notification services (for sending alerts via email, SMS, or push notifications) would be decoupled from the monitoring service and operate asynchronously. Alerts would be routed through external providers such as Twilio or AWS SES for high reliability and scalability.

Crucially, the monitoring and alerting service must be hosted on infrastructure that is separate from the services being monitored. If both go down simultaneously during a critical failure, the system would be unable to send alerts or respond to incidents. Therefore, it's essential to design for high availability, potentially running the monitoring service in a separate cloud region or using a disaster recovery setup. Comparatively, while services like PagerDuty offer advanced features such as incident management and detailed reporting, this design focuses on the fundamental components needed for real-time alerting: gathering metrics, analyzing data for alerts, and delivering notifications through configurable channels.

There is significant overlap with a question asking about generic metrics and logging services:

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