Consistency and Reconciliation 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. Visible writes have VCs [1,0] and [3,0], the latter latest. A read returns [2,0] with context [1,0]. Which course label applies? Select one answer.

Select one answer.

eventual causal linearizable Concurrent

2. Every read in a finite exercise trace receives the fallback label eventual. What has been established? Select one answer.

Select one answer.

The replicas are guaranteed to converge after the trace The stronger per-read checks failed; convergence has not been demonstrated Every execution of this service is eventually consistent The reads all observed the newest completed write

3. Latest=50, window=3. Healthy replicas are ID 4: applied 47 latency 9; ID 2: applied 48 latency 9; ID 1: applied 46 latency 1. Which ID is chosen? Enter one integer.

4. Mathematical lag is MaxInt+1; window is MaxInt and fallback is disabled. What is the plan mode? Select one answer.

Select one answer.

bounded, after clamping lag to MaxInt fallback none bounded, because the subtraction is negative

5. A has VC [4,0], timestamp 7; B has VC [2,2], timestamp 9. Their payloads differ. Which relation/resolution pair follows? Select one answer.

Select one answer.

B / B A / A equal / merge-required conflict / B

6. A repair action is {FromReplica:7, ToReplica:2}. What should it mean at execution? Select one answer.

Select one answer.

Replica 7 fetches the winning version from replica 2 Replica 2 replaces its winner with replica 7’s stale value Both replicas discard their versions The action proves all concurrent versions have been installed

7. For one key: write 9, write 2, read 5. What is FirstRYWViolation (zero-based)? Enter one integer.

8. Two non-dominated replicas have VCs [2,1] and [2,1,0] but different payloads. What does this planner retain? Select one answer.

Select one answer.

Only the smallest ID Both as winners Only the largest ID Neither, because equal VCs are invalid

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