Fastly CDN: Technical Reference and Operational Intelligence

Core Value Proposition

Primary Advantage: 150ms global cache purging vs competitors' 10-15 minute delays
Cost Impact: 3x more expensive than Cloudflare, similar premium over other CDNs
Break-even Point: When cache invalidation delays cost more than premium pricing

Performance Specifications

Cache Purging Performance

• Fastly: 150ms globally (consistently under 200ms)
• CloudFront: 10-15 minutes
• Cloudflare: 30 seconds
• Akamai: 2-5 minutes

Network Architecture

• POPs: ~70 locations with high-capacity hardware
• Connection Speed: 100+ Gbps per location
• Cache Hit Ratio: 92% typical (vs 78% on CloudFront)
• Trade-off: 50-100ms further from users vs Cloudflare's 300+ smaller locations

Edge Compute Performance

• Startup Time: <1ms (WebAssembly)
• Languages Supported: Rust, Go, C++, JavaScript/TypeScript, Python
• Performance Gain: 200ms latency reduction when moving auth logic to edge
• First 20ms: CPU time free per request

Cost Structure and Budget Reality

Pricing Breakdown

• Base Bandwidth: $0.12/GB North America, $0.28-0.34 elsewhere
• Requests: $0.75 per million
• Edge Compute: $0.50 per million requests + memory/CPU charges
• "Free" Tier: $50 monthly credit (≈400GB traffic)

Real-World Cost Examples

• 1TB/month site: $150-200/month minimum
• 2TB/month site: $280/month actual
• Traffic spike impact: $80 → $600 during Reddit front-page event

Cost Comparison Matrix

Provider	Monthly Range	Cache Purge	Learning Curve	Bill Shock Risk
Fastly	$200-500	150ms	Weekend	High
Cloudflare	$20-50	30s	Hours	Low
CloudFront	$50-200	10-15min	Weeks	Very High
Akamai	$500+	2-5min	Consultant	Quote-based

Critical Implementation Warnings

Bill Shock Prevention

• Root Cause: Usage-based pricing scales with every byte
• Trigger Events: Traffic spikes, viral content, DDoS attacks
• Mitigation: Set billing alerts, budget 3x normal costs for spikes
• Finance Challenge: Explaining why successful launches increase CDN costs

Production Failure Scenarios

• Cache Invalidation Delays: Cost $3K-5K during pricing bug incident (20-minute CloudFront delay)
• Origin Server Dependency: CDN failures require direct traffic handling capability
• Historical Outage Impact: June 2021 incident affected "half the internet" for 1 hour

Configuration Complexity

• VCL Requirement: Advanced features need custom VCL configuration
• Migration Time: 2-3 days minimum for proper setup from other CDNs
• Debugging Challenge: Edge function debugging "sucks" during incidents

Decision Criteria Framework

Use Fastly When:

• E-commerce: Frequent pricing changes, inventory updates
• News/Media: Breaking stories require instant cache invalidation
• High-Traffic APIs: >1M requests/day benefit from edge compute
• Revenue Impact: Downtime costs >$1000/minute
• Cache Sensitivity: 150ms vs 15 minutes affects business metrics

Don't Use Fastly When:

• Static Sites: WordPress blogs, marketing sites
• Low Traffic: <1TB/month handled adequately by cheaper alternatives
• Budget Constraints: Cannot absorb 3x cost increase
• Simple Needs: Basic CDN functionality sufficient

Technical Capabilities

Security Features

• Next-Gen WAF: Acquired Signal Sciences product, $1,500/month minimum
• DDoS Protection: Layer 3/4 filtering included, Layer 7 rate limiting
• Bot Detection: ML-based, better than regex but not perfect

Real-Time Operations

• Log Streaming: Sub-second delivery to Elasticsearch, Splunk, S3
• Analytics: Real-time cache hit ratios, error rates, geographic distribution
• API Quality: "Clean & simple" with working examples
• Configuration Deployment: Instant via API (vs 20-minute AWS waits)

Storage Options

• Config Store: Configuration data at edge
• KV Store: Application data with sub-millisecond lookups
• Secret Store: API keys and credentials

Resource Requirements

Implementation Time

• Basic Setup: Weekend project
• Advanced Configuration: Requires VCL knowledge
• Migration from Other CDNs: 2-3 days minimum

Expertise Requirements

• Basic Use: Standard CDN configuration knowledge
• Advanced Features: VCL programming for custom logic
• Debugging: Significant challenge for edge function issues

Support Quality

• Documentation: "Solid" and comprehensive
• Community: Smaller than Cloudflare's
• Enterprise Support: Dedicated for high-tier customers
• Standard Support: "Mostly on your own" for complex configurations

Competitive Positioning

Market Position

• Strategy: Premium speed vs budget optimization
• Customer Base: GitHub, Shopify, The Guardian
• Volume Threshold: $10K+ monthly spend for meaningful enterprise discounts

Technology Differentiators

• WebAssembly Edge: Only CDN supporting compiled languages at edge
• Hardware Approach: Fewer, more powerful locations vs distributed micro-POPs
• API Design: Immediate deployment vs eventual consistency models

This technical reference provides the operational intelligence needed for informed CDN selection and successful Fastly implementation while understanding the cost-benefit trade-offs and failure scenarios.