Observability ensures you can understand what’s happening inside your SaaS system. Monitoring ensures you act on those insights before users feel pain. This chapter explains logs, metrics, tracing, alerting, chaos testing, and AI-specific observability. Applied examples show how to evolve your Todo List SaaS from basic error tracking to enterprise-grade observability with distributed tracing and per-tenant dashboards.

1. Logs

Best Practices

• Centralize logs across services.
• Add Request ID and Tenant ID to every log line.
• Use structured logging (JSON).
• Rotate logs to avoid storage bloat.

Tools

• ELK Stack (Elasticsearch, Logstash, Kibana).
• Grafana Loki.
• AWS CloudWatch / GCP Logging.

Real-Life Example

• Uber uses structured logs with correlation IDs to debug microservices at scale.

Todo List SaaS Setup

• MVP: Console logs + Sentry.
• Growth: Centralized logs in Loki.
• Enterprise: ELK stack with per-tenant log dashboards.

2. Metrics