EO Engineering Learning OS
PROJECT LADDER · P09
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CORE PROJECT · TARGET L3–4 · 5–7 days
P09

Observability

Build evidence that supports detection, diagnosis and service decisions.

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

Structured logs

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

02

Metrics

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

03

Traces

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

04

Dashboards

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

05

Alerts

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

06

Runbooks

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

02 / SYSTEM FLOW

Trace it end to end.

Application event→collector→logs/metrics/traces→dashboard→alert→operator

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. 01Define service questions
  2. 02Add correlation IDs
  3. 03Create golden-signal metrics
  4. 04Build dashboard
  5. 05Create actionable alert
  6. 06Use evidence to solve an injected failure
04 / INCIDENT

Latency rises while CPU is normal; traces reveal database connection waiting.

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.

Define signals and alert ownership without creating noise.

06 / VERIFY, SUBMIT & REVIEW

Submission evidence

Architecture review

  • Explain observability 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