Coordination and Transactions Checkpoint

Trace fresh cases, diagnose plausible bugs, and separate the exercise model from production guarantees.

Get every question correct to pass this checkpoint. You can review feedback, revise your answers, and submit again.

1. Snapshots are a:timeout/unacked, b:commit/acked, a:commit/unacked. What plan follows? Select one answer.

Select one answer.

abort; retry a commit; retry a commit; retry a and b abort; retry nobody

2. A coordinator durably committed, notified one participant, then crashed. The recovered vote cache is incomplete. What must recovery use? Select one answer.

Select one answer.

A new abort because current votes are incomplete Whichever decision the fastest participant suggests The durable commit decision and idempotent notification retries A saga rollback of the participant already committed

3. Steps: reserve ok/release; audit skipped; charge ok/refund. All are compensable. What is planned? Select one answer.

Select one answer.

refund then release Nothing because skipped is not failed refund only release only

4. Steps: A ok/undoA eligible; B ok/undoB eligible; A ok but noncompensable; C failed. Result? Select one answer.

Select one answer.

undoB, then undoA undoB only undoA, then undoB undoA twice, then undoB

5. Operation x with token 2 is rejected before any grant. Token 2 is granted, then x is retried. Result? Select one answer.

Select one answer.

Accept because the token now matches Replay=true and the original no-grant rejection Reject stale-token with Replay=false Ignore x because rejected writes are never cached

6. Operation y was accepted under token 4. After grant 5, retry y arrives with token 4. What does accepted replay mean? Select one answer.

Select one answer.

Authorize a new token4 write despite fencing Delete the cached result and reject y Return the prior success without applying another write Roll back the original write

7. Latest granted token is 8. A fresh operation carries token 9. What does this simulator do? Select one answer.

Select one answer.

Accept because9 exceeds8 Advance the grant to9 and accept Replay the last token8 write Reject with stale-token reason

8. The planner returns refund then release. Which guarantee still requires an execution protocol? Select one answer.

Select one answer.

Persisting and retrying compensations without duplicating effects The list is in reverse retained order No action appears after the first failure boundary Each eligible step name appears at most once

Auto-advance on pass

Join Discord