A DevOps team is establishing automated cost governance for a sandbox Google Cloud project to prevent runaway expenses. The solution must satisfy the following technical and operational requirements: Trigger proactive notifications when spending trends project that the project will exceed its $2,000 monthly allocation before the calendar period ends. Automatically trigger a programmatic remediation runbook to scale down non-essential workloads or disable project billing when actual monthly spend reaches 100% of the allocated budget. Ensure the automated remediation pipeline receives JSON payloads that include structured threshold violation flags. Which configuration should the DevOps engineer implement?

Create a Cloud Billing budget scoped to the sandbox project with both Forecasted (>100%) and Actual (100%) spend threshold rules, connect the budget to a Cloud Pub/Sub topic, and subscribe an automated Cloud Function to process the payload and execute remediation actions.: What Cloud Billing Budgets with Programmatic Notifications Is Google Cloud Billing budgets allow organizations to track resource costs against defined monetary targets. When coupled with Cloud Pub/Sub, budget alerts become programmatic triggers that publish real-time budget status messages as structured JSON objects, enabling serverless automation like Cloud Functions or Cloud Run to act as automated remediation runbooks. How It Meets the Requirements Proactive Forecasted Alerts: Defining a Forecasted spend threshold rule (e.g., >100%) allows the system to extrapolate current consumption trends out to the end of the calendar month and trigger alerts before the allocation is fully depleted. Automated Cost Control Actions: Connecting the budget to a Cloud Pub/Sub topic delivers status updates directly to an event-driven Cloud Function, which can make API calls to shut down Compute Engine instances, delete deployments, or detach the billing account (google.billing.v1.CloudBilling). Threshold Violation Flags in Payloads: Configuring explicit threshold alert rules (both Actual and Forecasted) guarantees that the published Pub/Sub JSON payload populates the alertThresholdExceeded and forecastThresholdExceeded fields for downstream parsing. Key Advantages and Capabilities Event-Driven Financial Governance: Decouples billing observation from workload lifecycle management using standard asynchronous pub/sub messaging. Predictive Anomaly Detection: Leverages Google Cloud's internal spend projection models to detect anomalous spikes prior to hard budget exhaustion. Granular Automation: Enables custom logic within the Cloud Function to conditionally scale down staging/sandbox infrastructure instead of causing abrupt service outages. High Precision: The Pub/Sub JSON message delivers precise metadata including costAmount, budgetAmount, and current billing period dates. Why This Is Optimal Cloud Billing budgets do not natively cap infrastructure or enforce hard billing limits out of the box. Using Pub/Sub programmatic notifications with threshold rules is the official, Google-recommended pattern for building automated cost capping, shutdown runbooks, and proactive alerting pipelines.