acedergren/oci-agent-skills/finops-cost-optimization

# Default OCI behavior: Boot volumes PRESERVED after instance termination
oci compute instance terminate --instance-id <ocid> --force
# Instance deleted, but boot volume remains (charges continue!)
 
Cost trap:
- Boot volume: 50 GB × $0.025/GB/mo = $1.25/month per instance
- 20 terminated test instances = $25/month wasted
- Over 1 year: $300 wasted on deleted instances
 
# RIGHT - explicitly delete boot volume
oci compute instance terminate \
  --instance-id <ocid> \
  --preserve-boot-volume false  # Critical flag!
 
# Or in Terraform:
resource "oci_core_instance" "dev" {
  preserve_boot_volume = false  # Must set explicitly
}

Cost: $0.01/hour = $7.30/month per IP
 
# Common mistake: Reserve IP, detach from instance, forget to release
oci network public-ip create --lifetime RESERVED
# Later: delete instance but IP remains reserved (charges continue)
 
Wasted cost example:
- 5 old reserved IPs from deleted instances
- 5 × $7.30/month = $36.50/month waste
- Over 1 year: $438 wasted
 
# RIGHT - use ephemeral IPs for temporary resources
oci network public-ip create --lifetime EPHEMERAL
# Auto-deleted when instance terminated
 
# Or release reserved IPs explicitly
oci network public-ip delete --public-ip-id <ocid>

Stopped Autonomous Database:
✓ Compute: Zero cost (stopped)
✗ Storage: $0.025/GB/mo continues
✗ Backups: Retention charges continue
 
Example: 1 TB ADB stopped for 30 days
Storage: 1000 GB × $0.025 = $25/month (charged!)
 
Stopped Compute Instance:
✓ Compute: Zero cost
✗ Boot volume: $0.025/GB/mo continues
✗ Block volumes: $0.025/GB/mo continues
✗ Reserved IP (if attached): $7.30/month continues
 
# Better for long-term idle (>30 days): TERMINATE + backup
# Restore from backup when needed

OCI egress pricing:
- First 10 TB/month: FREE
- 10-50 TB: $0.0085/GB
- 50+ TB: Contact sales for discount
 
# Common mistake: Large data export
oci os object bulk-download --bucket-name backups --download-dir /local
# Downloading 15 TB = 5 TB chargeable × $0.0085/GB = $42,500 surprise!
 
# Cheaper alternatives:
1. Use OCI FastConnect (fixed cost, unlimited egress)
2. Download within same region (free between OCI services)
3. Export to another OCI region first (inter-region = free)
 
Cost comparison (15 TB export):
- Internet egress: $42,500
- FastConnect (1 Gbps): $1,100/month flat rate
- Breakeven: 130 GB/month egress

NAT Gateway pricing:
- Gateway itself: $0.01/hour = $7.30/month
- Data processed: $0.01/GB
 
# Mistake: Use NAT Gateway for high-traffic apps
Example: Application with 5 TB/month outbound traffic
- Gateway: $7.30/month
- Data: 5000 GB × $0.01 = $50/month
- Total: $57.30/month
 
# Cheaper alternative: Public IP on instance (ephemeral IP = free)
Cost: $0/month for egress <10 TB
 
When NAT Gateway makes sense:
- Private subnets with <100 GB/month egress
- Security requirement (no public IPs on instances)
 
When to avoid:
- High-traffic egress (use public IPs instead)
- Low-security dev/test environments

Universal Credits gotcha:
- Credits are NON-TRANSFERABLE between service categories
  * Compute credits → can only pay for compute
  * Database credits → can only pay for database
  * Cannot move credits between categories
 
# Mistake: Commit to $10k/month compute credits
# Reality: Only use $6k/month compute
# Cannot use $4k surplus for database spending
# Result: Waste $4k/month ($48k/year)
 
# RIGHT - commit conservatively based on baseline usage
Analyze 3-6 months historical usage
Commit to 70-80% of baseline (not peak)
 
Expiration gotcha:
- Monthly credits expire end of month
- Cannot roll over to next month
- Use-it-or-lose-it model

OCI Budget types:
1. ACTUAL: Alerts on actual spending (accurate)
2. FORECAST: Alerts on projected spending (often wrong)
 
# Problem: Forecast uses simple linear projection
Example:
- Week 1: $100 spend
- Forecast for month: $100 × 4 = $400
- Reality: Week 1 included one-time data migration
- Actual month: $150 total
- Forecast error: 167% over-prediction
 
# WRONG - rely on forecast alerts
Alert at 80% forecast → fires prematurely
 
# RIGHT - use actual spend alerts at multiple thresholds
Alert at 50% actual, 75% actual, 90% actual, 100% actual

Legacy fixed shape:
VM.Standard2.4: 4 OCPUs, 60 GB RAM (fixed ratio 1:15)
Cost: $0.06/hr × 4 = $0.24/hr = $175/month
 
Flex shape (right-sized):
VM.Standard.E4.Flex: 4 OCPUs, 16 GB RAM (custom ratio)
Cost: ($0.02/OCPU-hr × 4) + ($0.0015/GB-hr × 16) = $0.104/hr = $76/month
 
Savings: $99/month per instance (56% reduction)
 
Migration path:
1. Create flex instance with same OCPU count
2. Test with minimal RAM (4 GB per OCPU)
3. Increase RAM only if needed
4. Delete fixed instance

AMD instance:
VM.Standard.E4.Flex: 4 OCPUs, 16 GB RAM
Cost: $0.02/OCPU-hr × 4 × 730 = $58.40/month
 
Arm instance (same workload):
VM.Standard.A1.Flex: 4 OCPUs, 16 GB RAM
Cost: $0.01/OCPU-hr × 4 × 730 = $29.20/month
 
Savings: $29.20/month per instance (50% reduction)
 
Gotcha: ARM64 architecture (not all apps compatible)
Check: Docker images available for ARM64?

Always-Free tier value if fully utilized:
 
Compute:
- 2 AMD Micro VMs: 2 × $7/month = $14/month
- 4 Arm OCPUs (24 GB): 4 × $7.30/month = $29.20/month
Subtotal: $43.20/month
 
Database:
- 2 Autonomous Databases: 2 × $292/month = $584/month
 
Storage:
- 200 GB block: $5/month
- 10 GB object: $0.26/month
- 10 GB archive: $0.02/month
Subtotal: $5.28/month
 
Networking:
- 1 load balancer: $10/month
- 10 TB egress: $85/month
Subtotal: $95/month
 
TOTAL COST AVOIDED: $727.48/month ($8,730/year)

Scenario: 10 TB compliance data, accessed quarterly
 
Without tiering (all Standard):
10,000 GB × $0.0255/GB/mo = $255/month = $3,060/year
 
With tiering (Archive after 30 days):
Month 1 (Standard): 10,000 GB × $0.0255 = $255
Months 2-12 (Archive): 10,000 GB × $0.0024 × 11 = $264
Total year: $519
 
Savings: $2,541/year (83% reduction)
 
Lifecycle policy:
- Day 0-30: Standard (frequent access window)
- Day 31+: Archive (compliance retention)
- Retrieval cost: $0.01/GB (acceptable for quarterly access)

Scenario: 10 development instances, 2 OCPUs each
Running 24/7: 10 × 2 × $0.02/hr × 730 = $292/month
 
Auto-shutdown (weekdays 9am-6pm only):
Usage: 9 hours/day × 5 days = 45 hours/week = 195 hours/month
Cost: 10 × 2 × $0.02/hr × 195 = $78/month
 
Savings: $214/month (73% reduction)
 
Implementation:
1. Tag instances: Environment=Development
2. Create Functions for start/stop
3. Schedule with OCI Events:
   - Start: Weekdays 9am
   - Stop: Weekdays 6pm

Scenario: Commit to $5k/month database credits
Month 1-3: Use only $3k/month (waste $2k/month)
Cannot: Transfer $2k to compute spending
Result: Waste $6k over 3 months
 
Better approach:
1. Analyze 6 months baseline usage per category
2. Commit to 70% of baseline (room for variance)
3. Over-commit only if growth guaranteed

Problem: How to allocate costs for shared VCN?
 
VCN costs:
- DRG: $0.01/hr = $7.30/month
- NAT Gateway: $0.01/hr + $0.01/GB = variable
- FastConnect: $1,100/month (1 Gbps)
 
Allocation strategies:
1. Equal split: $1,107.30 / N teams
2. Usage-based: Track egress per team (requires tagging)
3. Chargeback: Production pays 100%, dev/test free
 
Gotcha: OCI doesn't auto-allocate shared resource costs
Must implement manual showback/chargeback process

Problem: Multiple apps share 1 load balancer
 
LB costs:
- Flexible LB: $10/month + $0.008/LCU-hour
- Bandwidth: $0.01/GB processed
 
Allocation approach:
1. Tag backends by team (freeform_tags.Team)
2. Estimate traffic % per team (monitoring metrics)
3. Allocate LB cost proportionally
 
Example:
- Total LB cost: $50/month
- Team A: 60% traffic → $30/month
- Team B: 40% traffic → $20/month

# Best practice: Set 4 alert levels
oci budgets alert-rule create \
  --budget-id <ocid> \
  --type ACTUAL \
  --threshold 50 \
  --recipients "team@example.com"
 
oci budgets alert-rule create \
  --budget-id <ocid> \
  --type ACTUAL \
  --threshold 80 \
  --recipients "team@example.com,manager@example.com"