optimizing-costs

# Cost Optimization

## Purpose

Cloud cost optimization transforms uncontrolled spending into strategic resource allocation through the FinOps lifecycle: Inform, Optimize, and Operate. This skill provides decision frameworks for commitment-based discounts (Reserved Instances, Savings Plans), right-sizing strategies, Kubernetes cost management, and automated cost governance across multi-cloud environments.

## When to Use This Skill

Invoke cost-optimization when:
- Reducing cloud spend by 15-40% through systematic optimization
- Implementing cost visibility dashboards and allocation tracking
- Establishing budget alerts and anomaly detection
- Optimizing Kubernetes resource requests and cluster efficiency
- Managing Reserved Instances, Savings Plans, or Committed Use Discounts
- Automating idle resource cleanup and right-sizing recommendations
- Setting up showback/chargeback models for internal teams
- Preventing cost overruns through CI/CD cost estimation (Infracost)
- Responding to finance team requests for cloud cost reduction

## FinOps Principles

### The FinOps Lifecycle

```
┌─────────────────────────────────────────────────────┐
│  INFORM → OPTIMIZE → OPERATE (continuous loop)      │
│    ↓         ↓           ↓                          │
│ Visibility  Action   Automation                     │
└─────────────────────────────────────────────────────┘
```

**Inform Phase:** Establish cost visibility
- Enable cost allocation tags (Owner, Project, Environment)
- Deploy real-time cost dashboards for engineering teams
- Integrate cloud billing data (AWS CUR, Azure Consumption API, GCP BigQuery)
- Set up Kubernetes cost monitoring (Kubecost, OpenCost)

**Optimize Phase:** Take action on cost drivers
- Purchase commitment-based discounts (40-72% savings)
- Right-size over-provisioned resources (target 60-80% utilization)
- Implement spot/preemptible instances for fault-tolerant workloads
- Clean up idle resources (unattached volumes, old snapshots)

**Operate Phase:** Automate and govern
- Budget alerts with cascading notifications (50%, 75%, 90%, 100%)
- Automated cleanup scripts for idle resources
- CI/CD cost estimation to prevent surprise increases
- Continuous monitoring with anomaly detection

### Core FinOps Principles

1. **Collaboration:** Cross-functional teams (finance, engineering, operations, product)
2. **Accountability:** Teams own the cost of their services
3. **Transparency:** All costs visible and understandable to stakeholders
4. **Optimization:** Continuous improvement of cost efficiency

For detailed FinOps maturity models and organizational structures, see `references/finops-foundations.md`.

## Cost Optimization Strategies

### 1. Commitment-Based Discounts

**Reserved Instances (RIs):** 40-72% discount for 1-3 year commitments
- **Standard RI:** Instance type locked, highest discount (60% for 3-year)
- **Convertible RI:** Flexible instance types, moderate discount (54% for 3-year)
- **Use for:** Databases (RDS, ElastiCache), stable production EC2 workloads

**Savings Plans:** Flexible compute commitments
- **Compute Savings Plans:** Applies to EC2, Fargate, Lambda (54% discount for 3-year)
- **EC2 Instance Savings Plans:** Tied to instance family (66% discount for 3-year)
- **Use for:** Workloads that change instance types or regions

**GCP Committed Use Discounts (CUDs):** 25-70% discount
- **Resource-based CUDs:** Commit to vCPU, memory, GPUs
- **Spend-based CUDs:** Commit to dollar amount (flexible)
- **Sustained Use Discounts:** Automatic 20-30% discount for sustained usage (no commitment)

**Decision Framework:**
```
Reserve when:
├─ Workload is production-critical (24/7 uptime required)
├─ Usage is predictable (stable baseline over 6+ months)
├─ Architecture is stable (unlikely to change instance types)
└─ Financial commitment acceptable (1-3 year lock-in)

Use On-Demand when:
├─ Development/testing environments
├─ Unpredictable spiky workloads
├─ Short-term projects (<6 months)
└─ Evaluating new instance types
```

For detailed commitment strategies and RI coverage analysis, see `references/commitment-strategies.md`.

### 2. Spot and Preemptible Instances

**Discount:** 70-90% off on-demand pricing (interruptible with 2-minute warning)

**Use Spot For:** CI/CD workers, batch jobs, ML training (with checkpointing), Kubernetes workers, data analytics
**Avoid Spot For:** Stateful databases, real-time services, long-running jobs without checkpointing

**Best Practices:**
- Diversify instance types and spread across Availability Zones
- Implement graceful shutdown handlers
- Auto-fallback to on-demand when capacity unavailable
- Kubernetes: Mix 70% spot + 30% on-demand nodes with taints/tolerations

### 3. Right-Sizing Strategies

**Target Utilization:** 60-80% average (leave headroom for spikes)

**Compute Right-Sizing:**
- Analyze actual CPU/memory utilization over 30+ days
- Downsize instances with <40% average utilization
- Consolidate underutilized workloads
- Switch instance families (compute-optimized vs. memory-optimized)

**Database Right-Sizing:**
- Analyze connection pool usage (max connections vs. allocated)
- Downgrade storage IOPS if utilization <50%
- Evaluate read replica necessity (can caching replace it?)
- Consider serverless options (Aurora Serverless, Azure SQL Serverless)

**Kubernetes Right-Sizing:**
- Set requests = average usage (not peak)
- Set limits = 2-3x requests (allow bursting)
- Use Vertical Pod Autoscaler (VPA) for automated recommendations
- Identify pods with 0% CPU usage (candidates for consolidation)

**Storage Right-Sizing:**
- Delete unattached volumes (EBS, Azure Disks, GCP Persistent Disks)
- Delete old snapshots (>90 days, retention policy not required)
- Implement lifecycle policies (S3 Intelligent-Tiering, Azure Blob Lifecycle)
- Compress/deduplicate data

**Right-Sizing Tools:**
- **AWS Compute Optimizer:** ML-based EC2, Lambda, EBS recommendations
- **Azure Advisor:** VM rightsizing, reserved instance advice
- **G