EO Engineering Learning OS
PROJECT LADDER · P06
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CORE PROJECT · TARGET L3–4 · 7–10 days
P06

Private AWS architecture + S3

Build a three-tier system with private compute/data, identity-based S3 access and per-user file ownership.

01 / CONCEPT MAP

Know what the parts mean.

Learn each concept deeply enough to recognize it, place it in the system and reason about normal and failed behavior.

01

VPC and subnets

Define it · locate it · observe it · explain its failure mode.

02

Routing and NAT

Define it · locate it · observe it · explain its failure mode.

03

Private EC2 and RDS

Define it · locate it · observe it · explain its failure mode.

04

IAM roles

Define it · locate it · observe it · explain its failure mode.

05

Private S3

Define it · locate it · observe it · explain its failure mode.

06

JWT ownership checks

Define it · locate it · observe it · explain its failure mode.

02 / SYSTEM FLOW

Trace it end to end.

Internet→Nginx / entry→Private EC2→RDS→IAM role→private S3

For every transition: identify input, output, identity, protocol, state, trust boundary, evidence and owner.

03 / GUIDED BUILD

Build, observe and explain.

Documentation and AI are allowed. The engineer must review every output and demonstrate the result from direct evidence.

  1. 01Draw the three-tier design
  2. 02Build network manually
  3. 03Deploy private application and RDS
  4. 04Attach narrow EC2 role
  5. 05Implement user-scoped upload/list/download
  6. 06Break routing and IAM deliberately
04 / INCIDENT

File uploads fail with AccessDenied while the application and database remain healthy.

Required investigation

State impact → collect evidence → form competing hypotheses → test the cheapest discriminator → isolate root cause → contain → correct → verify.

Evidence pack

Timeline, relevant logs/metrics, failed assumptions, root cause, correction, verification and one prevention action.

AI ownership

AI may suggest causes and commands. The engineer must explain why each check is safe, what result is expected and how the result changes the hypothesis.

05 / DESIGN CHALLENGE

Defend the decision.

Defend public/private placement, NAT need, S3 endpoint option and IAM boundaries.

06 / VERIFY, SUBMIT & REVIEW

Submission evidence

Architecture review

  • Explain private aws architecture + s3 without relying on memorized commands.
  • Draw the flow and name what crosses every arrow.
  • Identify the most likely, highest-impact and hardest-to-detect failure.
  • Show the evidence that proves the solution works.
  • Defend one security, reliability and cost trade-off.

Definition of Done

  • Acceptance criteria pass
  • Flow is drawn and explained
  • Security implications considered
  • Logs/metrics checked
  • Failure is tested
  • AI output is understood
  • Runbook is reusable
  • Mentor review passes
07 / MENTOR GUIDE

Do not score memory. Score the engineer’s ability to form a model, collect evidence, make a safe change and defend the trade-off.

1 Cannot explain2 Understands with gaps3 Implements and troubleshoots4 Designs and reviews