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Grade 11 · unit review

Review: Design a Reliable Request Workflow

Two increment requests read count 5 and both write 6. Explain the defect, a preservation strategy and a bounded retry policy with delays 1,2,4 seconds.

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Unit review questions
1. Reject count 25 before updating. Which check or operation is described?
Need a hint?
  • Check syntax, input contract and authorization before the permitted state change.
  • A200-like response label cannot replace verification of the saved result.
2. Create another row on every request. Which specific repeated-request mechanism does the supplied model describe?
Need a hint?
  • Compare the intended stored state after one operation with the state after repeating that same operation.
  • Idempotent does not mean the server produces identical responses or no logs.
3. Second write overwrites 6 with 6. Two intended increments start from 5. Classify the final evidence.
Need a hint?
  • Trace each read and write and compare the final value with the intended combined operation.
  • Two individually valid requests can still conflict when they share state.
4. Policy allows three retry delays of 4,8,16 seconds after the initial request. Total delay budget, excluding request time?
Need a hint?
  • Add the listed retry delays and respect the maximum attempt rule.
  • Retrying every failure indefinitely is not a reliability plan.

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Use the skills in a new task

Two increment requests read count 5 and both write 6. Explain the defect, a preservation strategy and a bounded retry policy with delays 1,2,4 seconds.

Work on paper or in your own document. Explain the choices you made.

  • Use only supplied fictional inputs and state the relevant rule.
  • Include labeled steps or evidence for each decision.
  • Name one limitation or tempting mistake.
  • Check that the result meets the task and revise a justified error.
Compare with a model response

Two increments should produce 7, but the model leaves 6, a lost update. Use an appropriate atomic or serialized update policy. Delays total 7 seconds, excluding request time. Repeated mutation needs documented safe effects or deduplication.

A different response can also meet the criteria. Compare the evidence and reasoning, rather than copying the wording.