GCP cost spikes: causes, checks, and alert policy.
GCP cost jumps often come from BigQuery query volume, autoscaling compute, project sprawl, or billing exports that no one reviews daily.
What usually moves the GCP bill
BigQuery queries scan more data after a dashboard, scheduled query, or analyst workflow changes.
Cloud Run, GKE, or Compute Engine scales during traffic bursts and stays above the previous run rate.
Vertex AI training, prediction, or model hosting shifts AI spend into the cloud bill.
Cloud Storage lifecycle policies miss old objects, snapshots, or backup exports.
Triage checklist
- Group billing export data by project, service, SKU, and label.
- Look for new SKUs or projects introduced during the spike window.
- Separate usage growth from pricing changes, discounts, and credits.
- Check BigQuery bytes processed and Vertex AI usage alongside cloud infrastructure.
Green, amber, red thresholds for GCP
Green
Daily GCP spend stays within 10% of baseline with no new high-cost SKUs.
Amber
Daily GCP spend is 10-25% above baseline, or a new project/SKU starts spending.
Red
Daily GCP spend is more than 25% above baseline or forecast crosses budget before month end.
Turn this playbook into a daily signal.
StackSpend connects GCP to your cloud and AI cost view with daily Slack or email reporting, anomaly detection, and pace-to-forecast.