Castai Cost Tuning

---
name: castai-cost-tuning
description: "'Maximize Kubernetes cost savings with CAST AI spot strategies and right-sizing. Use when analyzing cloud spend, optimizing spot-to-on-demand ratios, or configuring CAST AI for maximum savings. Trigger with phrases like \"cast ai cost\", \"cast ai savings\", \"cast ai spot strategy\", \"reduce kubernetes cost\", \"cast ai budget\". '"
allowed-tools: "Read, Write, Edit, Bash(curl:*), Grep"
category: devops-and-infra
source_repo: jeremylongshore/claude-code-plugins-plus-skills
source_path: "plugins/saas-packs/castai-pack/skills/castai-cost-tuning/SKILL.md"
source_url: https://github.com/jeremylongshore/claude-code-plugins-plus-skills/blob/HEAD/plugins/saas-packs/castai-pack/skills/castai-cost-tuning/SKILL.md
---

# CAST AI Cost Tuning

## Overview

Maximize Kubernetes cost savings through CAST AI: spot instance strategies, workload right-sizing, cluster hibernation, and savings tracking. Typical savings: 50-70% on cloud compute costs.

## Prerequisites

- CAST AI Phase 2 enabled with full automation
- Savings report available (requires 24h+ of data)
- Understanding of workload criticality tiers

## Instructions

### Step 1: Analyze Current Savings

```bash
# Get savings breakdown
curl -s -H "X-API-Key: ${CASTAI_API_KEY}" \
  "https://api.cast.ai/v1/kubernetes/clusters/${CASTAI_CLUSTER_ID}/savings" \
  | jq '{
    currentMonthlyCost: .currentMonthlyCost,
    optimizedMonthlyCost: .optimizedMonthlyCost,
    monthlySavings: .monthlySavings,
    savingsPercentage: .savingsPercentage,
    spotSavings: .spotSavings,
    rightSizingSavings: .rightSizingSavings
  }'
```

### Step 2: Maximize Spot Usage

```bash
# Enable aggressive spot with diversity and fallbacks
curl -X PUT -H "X-API-Key: ${CASTAI_API_KEY}" \
  -H "Content-Type: application/json" \
  "https://api.cast.ai/v1/kubernetes/clusters/${CASTAI_CLUSTER_ID}/policies" \
  -d '{
    "enabled": true,
    "spotInstances": {
      "enabled": true,
      "clouds": ["aws"],
      "spotDiversityEnabled": true,
      "spotDiversityPriceIncreaseLimitPercent": 20,
      "spotBackups": {
        "enabled": true,
        "spotBackupRestoreRateSeconds": 600
      }
    }
  }'
```

**Spot allocation strategy by workload tier:**

| Workload Type | Spot % | Rationale |
|---------------|--------|-----------|
| Batch jobs, CI runners | 100% spot | Interruptible, restartable |
| Stateless APIs (behind LB) | 80% spot | Can handle brief interruptions |
| Stateful services, databases | 0% spot | Use on-demand or reserved |
| ML training | 80-100% spot | Checkpointing handles interrupts |

### Step 3: Workload Right-Sizing

```bash
# Get resource waste analysis
curl -s -H "X-API-Key: ${CASTAI_API_KEY}" \
  "https://api.cast.ai/v1/workload-autoscaling/clusters/${CASTAI_CLUSTER_ID}/workloads" \
  | jq '[.items[] | select(.estimatedSavingsPercent > 20) | {
    name: .workloadName,
    namespace: .namespace,
    wastedCpu: (.currentCpuRequest - .recommendedCpuRequest),
    wastedMemory: (.currentMemoryRequest - .recommendedMemoryRequest),
    savingsPercent: .estimatedSavingsPercent
  }] | sort_by(-.savingsPercent) | .[0:10]'
```

### Step 4: Cluster Hibernation (Dev/Staging)

```bash
# Hibernate non-production clusters during off-hours
# Scales nodes to zero, resume on demand

# Enable hibernation
curl -X POST -H "X-API-Key: ${CASTAI_API_KEY}" \
  -H "Content-Type: application/json" \
  "https://api.cast.ai/v1/kubernetes/clusters/${CASTAI_CLUSTER_ID}/hibernate" \
  -d '{
    "schedule": {
      "enabled": true,
      "hibernateAt": "20:00",
      "wakeUpAt": "08:00",
      "timezone": "America/New_York",
      "weekdaysOnly": true
    }
  }'
```

### Step 5: Cost Tracking Dashboard

```typescript
interface CostReport {
  cluster: string;
  period: string;
  currentCost: number;
  optimizedCost: number;
  savings: number;
  spotPercent: number;
}

async function generateMonthlyCostReport(
  clusterIds: string[]
): Promise<CostReport[]> {
  const reports: CostReport[] = [];

  for (const clusterId of clusterIds) {
    const [cluster, savings, nodes] = await Promise.all([
      castaiGet(`/v1/kubernetes/external-clusters/${clusterId}`),
      castaiGet(`/v1/kubernetes/clusters/${clusterId}/savings`),
      castaiGet(`/v1/kubernetes/external-clusters/${clusterId}/nodes`),
    ]);

    const spotNodes = nodes.items.filter(
      (n: { lifecycle: string }) => n.lifecycle === "spot"
    ).length;

    reports.push({
      cluster: cluster.name,
      period: new Date().toISOString().slice(0, 7),
      currentCost: savings.currentMonthlyCost,
      optimizedCost: savings.optimizedMonthlyCost,
      savings: savings.monthlySavings,
      spotPercent:
        nodes.items.length > 0
          ? (spotNodes / nodes.items.length) * 100
          : 0,
    });
  }

  return reports;
}
```

## Cost Optimization Checklist

- [ ] Spot instances enabled with diversity
- [ ] Workload autoscaler right-sizing resources
- [ ] Dev/staging clusters hibernated off-hours
- [ ] Empty node downscaler enabled
- [ ] Instance families include latest generation (cheaper)
- [ ] Reserved/savings plan for baseline on-demand nodes
- [ ] Weekly savings report review

## Error Handling

| Issue | Cause | Solution |
|-------|-------|----------|
| Savings lower than expected | Too many on-demand constraints | Relax node template constraints |
| Spot interruptions too frequent | Single instance type | Enable spot diversity |
| Hibernation not triggering | Schedule timezone wrong | Use IANA timezone format |
| Right-sizing too aggressive | Low headroom | Increase memory headroom to 20% |

## Resources

- [CAST AI Savings Report](https://docs.cast.ai/docs/getting-started)
- [Spot Instance Best Practices](https://docs.cast.ai/docs/autoscaler-settings)
- [Cluster Hibernation](https://docs.cast.ai/docs/autoscaling-cluster-hibernation)

## Next Steps

For architecture patterns, see `castai-reference-architecture`.

---

**Source:** [`jeremylongshore/claude-code-plugins-plus-skills`](https://github.com/jeremylongshore/claude-code-plugins-plus-skills) → `plugins/saas-packs/castai-pack/skills/castai-cost-tuning/SKILL.md`