A hand-lettered cyanotype blueprint of a building renovation, white linework on Prussian blue

Planetek · AWS Boardwalk · Plank 9

Alpenglow Network Blueprint

The classic infrastructure interview, drawn and then built: a multi-AZ VPC with tiered subnets, layered security groups, stateless NACLs, and no NAT gateway anywhere. Private workloads reach S3 and DynamoDB through free gateway endpoints instead. Every line on this sheet is proven twice: AWS's own Reachability Analyzer checks the plan, and probe commands run on the instances walk the site. The stack is erected for demo windows and struck afterward; the as-built record below outlives it.

stack status
latest evidence
reachability verdicts as designed
live probes as designed
Sheet 01Site status
checking…

Reading /evidence/status.json

One command each way: make demo stakes out the whole network, runs the Reachability Analyzer paths, executes the probe suite, and files fresh evidence in about 15 minutes; make teardown strikes everything that bills (two instances, three interface endpoints, flow logs) and leaves this page serving the final report. Idle between windows: ~$0.

Sheet 02Plan view

The blueprint

Three subnet tiers across two availability zones. Traffic is admitted one hop at a time: 443 from the internet to the web tier, 8080 from web to app, 5432 from app to data. The private tiers have no route to the internet at all.

Internet (and its port scanners) Internet gateway net-igw NAT gateway struck from the drawing, $0 by design VPC 10.42.0.0/16 · us-east-1 flow logs: ALL traffic → CloudWatch AZ us-east-1a AZ us-east-1b public · 10.42.0.0/24 net-public-web · t4g.nano public IP · net-web-sg (443 ← world) IMDSv2 only · SSM-managed, no SSH public · 10.42.1.0/24 standing room for the web tier :443 ✓ app · 10.42.10.0/24 · private net-private-app · t4g.nano :8080 ← web SG only · no internet path PrivateLink: ssm · ssmmessages · ec2messages app · 10.42.11.0/24 · private multi-AZ capacity, same tier rules :8080 ✓ :5432 ✗ data · 10.42.20.0/24 · private net-data-sg: 5432 ← app SG only tier defined · deliberately vacant data · 10.42.21.0/24 · private Amazon S3 public service, no internet used DynamoDB public service, no internet used Gateway endpoints prefix-list routes · FREE app + data route tables ✓ no route ✗

Both instances are managed exclusively through SSM; no SSH port exists anywhere in the VPC. The public one registers over the internet, the private one through the three PrivateLink interface endpoints ($0.01/hr each: the plank's main running cost, and the reason it tears down between windows).

Sheet 03Field inspection

Send the inspector on a round

While the stack is staked out you can walk the site yourself. A round runs the eight probe commands on the two live instances via SSM Run Command, one at a time, and closes by checking the field results against the four Reachability Analyzer verdicts from the plan check. The blocked paths are part of the round: watching them fail on cue is the point. One inspector is out at a time; if a round is already under way you are handed that one to watch instead.

Checking whether the site is staked out…

Dispatchthe work order is picked up Web tier3 probes, in from the street App tier5 probes, in over PrivateLink Plan checkfield results vs analyzer Filedverdict in the day book

the field book opens when a round goes out (or pick a recent round below)

Recent rounds

Yours and other visitors'. Records expire after 48 hours; pick one to read its field book back.

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Sheet 04As-built record

Latest evidence report

An architect's hands drawing on a technical plan with a pencil and a wooden scale rule
Every line gets checked twice: once at the drafting table, once on the site. Photo by Daniel McCullough (Unsplash).
Sheet 05General notes

What this plank proves