EO Engineering Learning OS
PROJECT LADDER · P15
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CORE PROJECT · TARGET L4 · 5 days
P15

Cost optimization

Connect architecture and usage to unit economics without degrading security or reliability.

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

Allocation

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

02

Utilization

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

03

Right-sizing

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

04

Commitments

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

05

Scheduling

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

06

Storage lifecycle

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

07

Unit cost

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

02 / SYSTEM FLOW

Trace it end to end.

Usage→allocation→cost→unit metric→optimization→verification

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. 01Establish cost baseline
  2. 02Allocate by component
  3. 03Find idle and oversized resources
  4. 04Model three options
  5. 05Implement one safe change
  6. 06Verify savings and service health
04 / INCIDENT

A cost-saving change causes throttling during peak demand.

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.

Balance variable demand, commitments, resilience and operational effort.

06 / VERIFY, SUBMIT & REVIEW

Submission evidence

Architecture review

  • Explain cost optimization 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