Tracing One Request Through Every Layer

~12 min read

A step-by-step walkthrough of exactly what happens between a user clicking a link and seeing the resulting page.

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Key points

  • DNS (Route 53 Alias) → CDN (CloudFront) → Load Balancer (ALB) → Compute (EC2/ASG) → Data (RDS/S3)
  • Cached static content short-circuits at the CDN layer, never reaching the origin at all
  • Only healthy instances (per ALB target group health checks) ever receive traffic
  • Credentials are retrieved at runtime from Secrets Manager, never hardcoded in application code