Amazon CloudFront: AI-Optimized Technical Reference

Configuration

Production-Ready Settings

• Cache Invalidation: Use versioned URLs (style-v1.2.3.css) instead of invalidations
  • Actual invalidation time: 15-28 minutes (not AWS's claimed 2 minutes)
  • Cost: $0.005 per invalidation path after first 1,000
• Price Classes: Use to limit expensive regions, can reduce bills by 30%
• Origin Shield: $0.0075 per 10,000 requests, essential for compute-heavy origins
• Edge Functions: Use CloudFront Functions (<1ms start) over Lambda@Edge (6-8 second cold starts)

Critical Infrastructure Requirements

• Three-tier architecture: Edge Locations → Regional Edge Caches → Origin
• 700+ edge locations: Performance varies drastically by region
• 13 regional edge caches: Add complexity and potential failure points
• Config propagation: 5-20 minutes for changes (plan deployments accordingly)

Resource Requirements

Cost Structure

Traffic Source	Cost per GB	Performance Quality
US East Coast	$0.085	Excellent
Europe	$0.085	Good
Asia Pacific	$0.140	Poor (3x cost, worse performance)

Time Investment

• Initial setup: Simple integration with existing AWS infrastructure
• Debugging cache behaviors: 3-6 hours typical for priority conflicts
• Global deployment testing: Essential before production
• Migration from competitors: Minimal if already in AWS ecosystem

Expertise Requirements

• Cache behavior configuration: High complexity, backwards priority system
• Terraform knowledge: Essential (CloudFormation templates are inadequate)
• Monitoring setup: Required to prevent 3am debugging sessions

Critical Warnings

Production Failure Modes

• Cache behavior priorities: Work backwards from expected logic
• Asian performance degradation: Singapore/Bangkok users report 8-second load times
• Lambda@Edge cold starts: Destroy authentication UX with random 6-8 second delays
• Free tier exhaustion: 1TB vanishes in under a week with real applications

Hidden Costs and Breaking Points

• Asian traffic premium: 3x multiplier not mentioned in basic pricing
• Request charges: Billed for failed requests, successful requests, and all variations
• Regional performance inequality: US excellent, Asia poor despite same configuration
• Cache invalidation delays: Marketing claims vs reality (2 minutes vs 28 minutes observed)

Common Implementation Failures

• Cache behavior rule conflicts: Rule #2 can override Rule #1 unexpectedly
• Geographic blocking limitations: Country-level only, no city-level blocking
• Edge location consistency: Some locations serve stale content for extended periods
• DDoS protection gaps: Shield Standard adequate, Shield Advanced ($3,000/month) only for frequent attacks

Decision Criteria

Choose CloudFront When

• Already deep in AWS ecosystem (S3, EC2, ALB integration)
• Need free data transfer from AWS services
• Require ACM SSL certificate integration
• Primary users in North America and Europe

Choose Alternatives When

• Cloudflare: Global performance priority, especially Asia
• Fastly: Premium performance requirements with budget
• KeyCDN: Budget constraints with acceptable performance

Monitoring and Operational Intelligence

Essential Metrics

• CacheMissRate: <15% target for most sites
• 4xxErrorRate and 5xxErrorRate: <1% target
• OriginLatency: Spikes indicate backend issues

Real-time Monitoring

• CloudWatch integration: Surprisingly effective
• Real-time logs to Kinesis: $0.01 per million log lines
• Sample at 1% to control costs
• Standard access logs to S3: Free (pay S3 storage only)

Performance Validation

• Test from multiple global locations before production
• Monitor Asian edge locations specifically for performance degradation
• Set up error rate alerts for cache behavior failures

Advanced Features with Gotchas

Origin Shield

• Purpose: Collapses multiple edge requests into single origin request
• Cost: $0.0075 per 10,000 requests
• Benefit: Prevents origin server overload from simultaneous requests
• Use case: Essential for image resizing APIs and compute-heavy origins

Security Features

• Shield Standard: Free, stops basic DDoS (tested against 50Gbps attack)
• Shield Advanced: $3,000/month with cost protection
• Signed URLs: Finicky signature generation, read documentation carefully

DevOps Integration

• Terraform provider: Use instead of CloudFormation
• AWS CLI wait commands: Essential for CI/CD pipeline stability
• Config change timing: Deploy CloudFront changes first, wait 15 minutes before application code

Competitive Analysis

Feature	CloudFront	Cloudflare	Assessment
Global Performance	US/EU good, Asia poor	Consistently fast globally	Cloudflare wins for global reach
AWS Integration	Seamless	External service	CloudFront wins for AWS shops
Cache Invalidation	15-28 minutes actual	Near-instantaneous	Cloudflare significantly better
Edge Functions	CF Functions fast, Lambda@Edge slow	Workers excellent	Cloudflare better execution
Asian Performance	Degraded, expensive	Consistent pricing/performance	Cloudflare superior

Migration Considerations

Breaking Points

• UI breaks at 1000 spans during debugging of large distributed transactions
• Edge location inconsistency makes debugging effectively impossible
• Cold start delays destroy user authentication experience
• Regional performance gaps cause user churn in affected markets

Success Patterns

• Versioned URL strategy eliminates invalidation dependencies
• Origin Shield prevents backend overload scenarios
• CloudFront Functions provide reliable sub-millisecond execution
• Terraform automation prevents configuration drift issues