cost-optimization

# Skill: Cost Optimization > **Expertise:** Cloud cost analysis, right-sizing recommendations, reserved/spot instances, tagging strategy, cost alerting. ## When to load When investigating unexpectedly high cloud bills, right-sizing instances, or setting up cost attribution by team/environment. ## Mandatory Cost Tags (every resource) ```hcl locals { cost_tags = { Project = var.project # e.g. "checkout" Environment = var.environment # prod / staging / dev Team = var.team # e.g. "backend-team" CostCenter = var.cost_center # e.g. "eng-platform" ManagedBy = "terraform" } } # Apply to every resource via merge(local.cost_tags, {...}) ``` ## AWS Cost Discovery ```bash # Top 10 most expensive services this month aws ce get-cost-and-usage \ --time-period Start=$(date +%Y-%m-01),End=$(date +%Y-%m-%d) \ --granularity MONTHLY \ --metrics BlendedCost \ --group-by Type=DIMENSION,Key=SERVICE \ --query 'ResultsByTime[0].Groups | sort_by(@, &Metrics.BlendedCost.Amount) | reverse(@) | [:10]' \ --output table # Cost by tag (Team) aws ce get-cost-and-usage \ --time-period Start=$(date +%Y-%m-01),End=$(date +%Y-%m-%d) \ --granularity MONTHLY \ --metrics BlendedCost \ --group-by Type=TAG,Key=Team # Idle EC2 instances (< 5% CPU, last 2 weeks) aws cloudwatch get-metric-statistics \ --namespace AWS/EC2 \ --metric-name CPUUtilization \ --dimensions Name=InstanceId,Value=<instance-id> \ --start-time $(date -d '-14 days' --iso-8601) \ --end-time $(date --iso-8601) \ --period 1209600 --statistics Average ``` ## Right-Sizing Workflow ```bash # Step 1: Get actual utilisation (Prometheus, last 7 days) # CPU: avg and p99 avg(avg_over_time(instance:node_cpu_utilisation:rate5m[7d])) by (instance) quantile_over_time(0.99, instance:node_cpu_utilisation:rate5m[7d]) # Memory: peak working set max_over_time(node_memory_MemUsed_bytes[7d]) / node_memory_MemTotal_bytes # Step 2: Recommendation formula # New CPU = p99_cpu × 1.3 (30% headroom) # New memory = peak_mem × 1.2 (20% headroom) # Step 3: Find next smaller instance type # AWS: use ec2-instance-selector ec2-instance-selector --vcpus-min 2 --vcpus-max 4 \ --memory-min 4 --memory-max 8 \ --region eu-west-1 \ --output table-wide ``` ## Reserved / Spot Instances ```hcl # Spot instances for non-critical worker nodes (60-80% savings) resource "aws_launch_template" "workers" { instance_market_options { market_type = "spot" spot_options { max_price = "0.10" # cap to avoid surprise costs spot_instance_type = "persistent" interruption_behavior = "terminate" } } } # Mixed: 70% spot, 30% on-demand for K8s node groups resource "aws_autoscaling_group" "workers" { mixed_instances_policy { instances_distribution { on_demand_base_capacity = 2 # always 2 on-demand on_demand_percentage_above_base_capacity = 30 # 30% on-demand, 70% spot spot_allocation_strategy = "capacity-optimized" } } } ``` ## Waste Detection Checklist ```bash # Unattached EBS volumes aws ec2 describe-volumes \ --filters Name=status,Values=available \ --query 'Volumes[*].{ID:VolumeId,Size:Size,Created:CreateTime}' \ --output table # Unused Elastic IPs aws ec2 describe-addresses \ --query 'Addresses[?AssociationId==null].{IP:PublicIp,AllocationId:AllocationId}' # Old snapshots (> 90 days, no associated AMI) aws ec2 describe-snapshots --owner-ids self \ --query 'Snapshots[?StartTime<`2024-08-01`].{ID:SnapshotId,Size:VolumeSize,Date:StartTime}' \ --output table # Unused load balancers (0 healthy targets) aws elbv2 describe-target-health \ --target-group-arn <arn> \ --query 'TargetHealthDescriptions[?TargetHealth.State==`unused`]' ``` ## Cost Alerting (AWS Budgets) ```hcl resource "aws_budgets_budget" "monthly_limit" { name = "${var.project}-${var.environment}-monthly" budget_type = "COST" limit_amount = var.monthly_budget_usd limit_unit = "USD" time_unit = "MONTHLY" notification { comparison_operator = "GREATER_THAN" threshold = 80 threshold_type = "PERCENTAGE" notification_type = "ACTUAL" subscriber_email_addresses = [var.billing_alert_email] } notification { comparison_operator = "GREATER_THAN" threshold = 100 threshold_type = "FORECASTED" notification_type = "FORECASTED" subscriber_email_addresses = [var.billing_alert_email] } } ``` ## K8s Cost Visibility (Kubecost / OpenCost) ```bash # Install OpenCost (open-source K8s cost allocation) helm install opencost opencost/opencost -n opencost --create-namespace # Query cost by namespace curl http://localhost:9003/allocation \ '?window=7d&aggregate=namespace&accumulate=true' | jq '.data[0]' # Cost by label (team) curl http://localhost:9003/allocation \ '?window=7d&aggregate=label:team&accumulate=true' ```