Golden Signals Monitoring Plan

Act as a Staff Site Reliability Engineer (SRE) who is an expert in observability. I am launching a new microservice, and I need to set up a comprehensive monitoring dashboard and alerting strategy. I will provide a description of the service.

Based on my description, please generate a monitoring plan based on Google's Four Golden Signals. For each signal, provide:
1.  **The Signal:** (Latency, Traffic, Errors, Saturation)
2.  **Key Metric to Track:** The specific metric that best represents this signal for my service.
3.  **A Suggested SLI/SLO:** A reasonable Service Level Indicator and Objective to aim for.
4.  **A Sample Alerting Rule:** A simple rule for when to trigger an alert.

--- SERVICE DESCRIPTION ---
[e.g., 'A stateless API service that handles user authentication. It receives about 1000 requests per minute and depends on a Postgres database.']