Data ETL Idempotency MCQ Questions with Answers (Latest 2026)

Q1. Which option best describes idempotency?

A. Operation that yields same result if applied multiple times. B. Random outcomes. C. Side effects on retry. D. Always non-deterministic.

Select an answer to check.

Answer: Operation that yields same result if applied multiple times.

Here, Operation that yields same result if applied multiple times. is the right choice. Critical for retries. It aligns directly with what the question asks about which option best describes idempotency. A quick elimination of partially true options helps confirm it.

Q2. What is the primary purpose of idempotency?

A. Random outcomes. B. Operation that yields same result if applied multiple times. C. Side effects on retry. D. Always non-deterministic.

Select an answer to check.

Answer: Operation that yields same result if applied multiple times.

In this case, Operation that yields same result if applied multiple times. is correct. Critical for retries. It aligns directly with what the question asks about what is the primary purpose of idempotency. A quick elimination of partially true options helps confirm it.

Q3. Which statement about idempotency is most accurate?

A. Side effects on retry. B. Always non-deterministic. C. Operation that yields same result if applied multiple times. D. Random outcomes.

Select an answer to check.

Answer: Operation that yields same result if applied multiple times.

The best option here is Operation that yields same result if applied multiple times.. Critical for retries. It aligns directly with what the question asks about which statement about idempotency is most accurate. A quick elimination of partially true options helps confirm it.

Q4. How is idempotency best characterized?

A. Side effects on retry. B. Random outcomes. C. Always non-deterministic. D. Operation that yields same result if applied multiple times.

Select an answer to check.

Answer: Operation that yields same result if applied multiple times.

For this question, Operation that yields same result if applied multiple times. is correct. Critical for retries. It aligns directly with what the question asks about how is idempotency best characterized. A quick elimination of partially true options helps confirm it.

Q5. Which option best describes idempotent writes?

A. Same input produces same target state on retry. B. Pure logs only. C. Random output. D. Insert always blindly.

Select an answer to check.

Answer: Same input produces same target state on retry.

Same input produces same target state on retry. is the correct answer here. Use keys + versions. It aligns directly with what the question asks about which option best describes idempotent writes. A quick elimination of partially true options helps confirm it.

Q6. What is the primary purpose of idempotent writes?

A. Random output. B. Pure logs only. C. Same input produces same target state on retry. D. Insert always blindly.

Select an answer to check.

Answer: Same input produces same target state on retry.

Here, Same input produces same target state on retry. is the right choice. Use keys + versions. This matches the core idea being tested around what is the primary purpose of idempotent writes. A quick elimination of partially true options helps confirm it.

Q7. Which statement about idempotent writes is most accurate?

A. Insert always blindly. B. Pure logs only. C. Same input produces same target state on retry. D. Random output.

Select an answer to check.

Answer: Same input produces same target state on retry.

In this case, Same input produces same target state on retry. is correct. Use keys + versions. This matches the core idea being tested around which statement about idempotent writes is most accurate. A quick elimination of partially true options helps confirm it.

Q8. How is idempotent writes best characterized?

A. Pure logs only. B. Random output. C. Same input produces same target state on retry. D. Insert always blindly.

Select an answer to check.

Answer: Same input produces same target state on retry.

The best option here is Same input produces same target state on retry.. Use keys + versions. This matches the core idea being tested around how is idempotent writes best characterized. A quick elimination of partially true options helps confirm it.

Q9. Which option best describes idempotency keys?

A. Random keys. B. No keys at all. C. Per-action keys to dedup writes. D. Pure timestamps only.

Select an answer to check.

Answer: Per-action keys to dedup writes.

For this question, Per-action keys to dedup writes. is correct. Common in APIs and ETL. This matches the core idea being tested around which option best describes idempotency keys. A quick elimination of partially true options helps confirm it.

Q10. What is the primary purpose of idempotency keys?

A. No keys at all. B. Pure timestamps only. C. Random keys. D. Per-action keys to dedup writes.

Select an answer to check.

Answer: Per-action keys to dedup writes.

Per-action keys to dedup writes. is the correct answer here. Common in APIs and ETL. This matches the core idea being tested around what is the primary purpose of idempotency keys. A quick elimination of partially true options helps confirm it.

Q11. Which statement about idempotency keys is most accurate?

A. Random keys. B. Pure timestamps only. C. No keys at all. D. Per-action keys to dedup writes.

Select an answer to check.

Answer: Per-action keys to dedup writes.

Here, Per-action keys to dedup writes. is the right choice. Common in APIs and ETL. That is exactly the concept behind which statement about idempotency keys is most accurate in this context. A quick elimination of partially true options helps confirm it.

Q12. How is idempotency keys best characterized?

A. Pure timestamps only. B. Per-action keys to dedup writes. C. No keys at all. D. Random keys.

Select an answer to check.

Answer: Per-action keys to dedup writes.

In this case, Per-action keys to dedup writes. is correct. Common in APIs and ETL. That is exactly the concept behind how is idempotency keys best characterized in this context. A quick elimination of partially true options helps confirm it.

Q13. Which option best describes UPSERT/MERGE?

A. INSERT only. B. DELETE only. C. Insert or update by key in one statement. D. UPDATE only.

Select an answer to check.

Answer: Insert or update by key in one statement.

The best option here is Insert or update by key in one statement.. Standard idempotent write. That is exactly the concept behind which option best describes upsert/merge in this context. A quick elimination of partially true options helps confirm it.

Q14. What is the primary purpose of UPSERT/MERGE?

A. INSERT only. B. DELETE only. C. UPDATE only. D. Insert or update by key in one statement.

Select an answer to check.

Answer: Insert or update by key in one statement.

For this question, Insert or update by key in one statement. is correct. Standard idempotent write. That is exactly the concept behind what is the primary purpose of upsert/merge in this context. A quick elimination of partially true options helps confirm it.

Q15. Which statement about UPSERT/MERGE is most accurate?

A. INSERT only. B. UPDATE only. C. Insert or update by key in one statement. D. DELETE only.

Select an answer to check.

Answer: Insert or update by key in one statement.

Insert or update by key in one statement. is the correct answer here. Standard idempotent write. That is exactly the concept behind which statement about upsert/merge is most accurate in this context. A quick elimination of partially true options helps confirm it.

Q16. How is UPSERT/MERGE best characterized?

A. INSERT only. B. UPDATE only. C. Insert or update by key in one statement. D. DELETE only.

Select an answer to check.

Answer: Insert or update by key in one statement.

Here, Insert or update by key in one statement. is the right choice. Standard idempotent write. It fits the requirement in the prompt about how is upsert/merge best characterized. A quick elimination of partially true options helps confirm it.

Q17. Which option best describes primary key + version?

A. Pure timestamp only. B. Stale events ignored vs current version. C. Pure primary key only. D. Pure log.

Select an answer to check.

Answer: Stale events ignored vs current version.

In this case, Stale events ignored vs current version. is correct. Avoids overwrites. It fits the requirement in the prompt about which option best describes primary key + version. A quick elimination of partially true options helps confirm it.

Q18. What is the primary purpose of primary key + version?

A. Stale events ignored vs current version. B. Pure primary key only. C. Pure timestamp only. D. Pure log.

Select an answer to check.

Answer: Stale events ignored vs current version.

The best option here is Stale events ignored vs current version.. Avoids overwrites. It fits the requirement in the prompt about what is the primary purpose of primary key. A quick elimination of partially true options helps confirm it.

Q19. Which statement about primary key + version is most accurate?

A. Pure primary key only. B. Stale events ignored vs current version. C. Pure log. D. Pure timestamp only.

Select an answer to check.

Answer: Stale events ignored vs current version.

For this question, Stale events ignored vs current version. is correct. Avoids overwrites. It fits the requirement in the prompt about which statement about primary key + version is. A quick elimination of partially true options helps confirm it.

Q20. How is primary key + version best characterized?

A. Pure log. B. Pure primary key only. C. Pure timestamp only. D. Stale events ignored vs current version.

Select an answer to check.

Answer: Stale events ignored vs current version.

Stale events ignored vs current version. is the correct answer here. Avoids overwrites. It fits the requirement in the prompt about how is primary key + version best characterized. A quick elimination of partially true options helps confirm it.

Q21. Which option best describes dedup by key + LSN?

A. Pure FIFO ordering. B. Random dedup. C. Drop earlier events for same key. D. Pure no dedup.

Select an answer to check.

Answer: Drop earlier events for same key.

Here, Drop earlier events for same key. is the right choice. Common in CDC sinks. This is the most accurate statement for which option best describes dedup by key +. A quick elimination of partially true options helps confirm it.

Q22. What is the primary purpose of dedup by key + LSN?

A. Drop earlier events for same key. B. Random dedup. C. Pure no dedup. D. Pure FIFO ordering.

Select an answer to check.

Answer: Drop earlier events for same key.

In this case, Drop earlier events for same key. is correct. Common in CDC sinks. This is the most accurate statement for what is the primary purpose of dedup by. A quick elimination of partially true options helps confirm it.

Q23. Which statement about dedup by key + LSN is most accurate?

A. Drop earlier events for same key. B. Pure FIFO ordering. C. Random dedup. D. Pure no dedup.

Select an answer to check.

Answer: Drop earlier events for same key.

The best option here is Drop earlier events for same key.. Common in CDC sinks. This is the most accurate statement for which statement about dedup by key + lsn. A quick elimination of partially true options helps confirm it.

Q24. How is dedup by key + LSN best characterized?

A. Random dedup. B. Pure FIFO ordering. C. Pure no dedup. D. Drop earlier events for same key.

Select an answer to check.

Answer: Drop earlier events for same key.

For this question, Drop earlier events for same key. is correct. Common in CDC sinks. This is the most accurate statement for how is dedup by key + lsn best. A quick elimination of partially true options helps confirm it.

Q25. Which option best describes at-least-once + idempotent sink?

A. At-most-once + retry. B. Duplicates removed by sink. C. Pure best-effort. D. At-most-once + dedup.

Select an answer to check.

Answer: Duplicates removed by sink.

Duplicates removed by sink. is the correct answer here. Effective exactly-once. This is the most accurate statement for which option best describes at-least-once + idempotent sink. A quick elimination of partially true options helps confirm it.

Q26. What is the primary purpose of at-least-once + idempotent sink?

A. Duplicates removed by sink. B. At-most-once + dedup. C. At-most-once + retry. D. Pure best-effort.

Select an answer to check.

Answer: Duplicates removed by sink.

Here, Duplicates removed by sink. is the right choice. Effective exactly-once. It aligns directly with what the question asks about what is the primary purpose of at-least-once +. The other options are either incomplete or contextually incorrect.

Q27. Which statement about at-least-once + idempotent sink is most accurate?

A. At-most-once + retry. B. At-most-once + dedup. C. Pure best-effort. D. Duplicates removed by sink.

Select an answer to check.

Answer: Duplicates removed by sink.

In this case, Duplicates removed by sink. is correct. Effective exactly-once. It aligns directly with what the question asks about which statement about at-least-once + idempotent sink is. The other options are either incomplete or contextually incorrect.

Q28. How is at-least-once + idempotent sink best characterized?

A. Duplicates removed by sink. B. At-most-once + dedup. C. Pure best-effort. D. At-most-once + retry.

Select an answer to check.

Answer: Duplicates removed by sink.

The best option here is Duplicates removed by sink.. Effective exactly-once. It aligns directly with what the question asks about how is at-least-once + idempotent sink best characterized. The other options are either incomplete or contextually incorrect.

Q29. Which option best describes retries with backoff?

A. No retries. B. Immediate retries forever. C. Re-attempts with growing delay. D. Random retries.

Select an answer to check.

Answer: Re-attempts with growing delay.

For this question, Re-attempts with growing delay. is correct. Pair with idempotency. It aligns directly with what the question asks about which option best describes retries with backoff. The other options are either incomplete or contextually incorrect.

Q30. What is the primary purpose of retries with backoff?

A. Random retries. B. Immediate retries forever. C. Re-attempts with growing delay. D. No retries.

Select an answer to check.

Answer: Re-attempts with growing delay.

Re-attempts with growing delay. is the correct answer here. Pair with idempotency. It aligns directly with what the question asks about what is the primary purpose of retries with. The other options are either incomplete or contextually incorrect.

Q31. Which statement about retries with backoff is most accurate?

A. No retries. B. Random retries. C. Re-attempts with growing delay. D. Immediate retries forever.

Select an answer to check.

Answer: Re-attempts with growing delay.

Here, Re-attempts with growing delay. is the right choice. Pair with idempotency. This matches the core idea being tested around which statement about retries with backoff is most. The other options are either incomplete or contextually incorrect.

Q32. How is retries with backoff best characterized?

A. Random retries. B. No retries. C. Immediate retries forever. D. Re-attempts with growing delay.

Select an answer to check.

Answer: Re-attempts with growing delay.

In this case, Re-attempts with growing delay. is correct. Pair with idempotency. This matches the core idea being tested around how is retries with backoff best characterized. The other options are either incomplete or contextually incorrect.

Q33. Which option best describes transactional writes?

A. Per-row writes only. B. All-or-nothing across rows/operations. C. Pure best-effort. D. Random ordering.

Select an answer to check.

Answer: All-or-nothing across rows/operations.

The best option here is All-or-nothing across rows/operations.. Maintains invariants. This matches the core idea being tested around which option best describes transactional writes. The other options are either incomplete or contextually incorrect.

Q34. What is the primary purpose of transactional writes?

A. Per-row writes only. B. All-or-nothing across rows/operations. C. Random ordering. D. Pure best-effort.

Select an answer to check.

Answer: All-or-nothing across rows/operations.

For this question, All-or-nothing across rows/operations. is correct. Maintains invariants. This matches the core idea being tested around what is the primary purpose of transactional writes. The other options are either incomplete or contextually incorrect.

Q35. Which statement about transactional writes is most accurate?

A. Pure best-effort. B. Per-row writes only. C. All-or-nothing across rows/operations. D. Random ordering.

Select an answer to check.

Answer: All-or-nothing across rows/operations.

All-or-nothing across rows/operations. is the correct answer here. Maintains invariants. This matches the core idea being tested around which statement about transactional writes is most accurate. The other options are either incomplete or contextually incorrect.

Q36. How is transactional writes best characterized?

A. All-or-nothing across rows/operations. B. Pure best-effort. C. Random ordering. D. Per-row writes only.

Select an answer to check.

Answer: All-or-nothing across rows/operations.

Here, All-or-nothing across rows/operations. is the right choice. Maintains invariants. That is exactly the concept behind how is transactional writes best characterized in this context. The other options are either incomplete or contextually incorrect.

Q37. Which option best describes two-phase commit?

A. Single-system commit. B. Coordinated commit across systems. C. Pure best-effort. D. Random commits.

Select an answer to check.

Answer: Coordinated commit across systems.

In this case, Coordinated commit across systems. is correct. Heavy; rarely used in modern ETL. That is exactly the concept behind which option best describes two-phase commit in this context. The other options are either incomplete or contextually incorrect.

Q38. What is the primary purpose of two-phase commit?

A. Random commits. B. Pure best-effort. C. Coordinated commit across systems. D. Single-system commit.

Select an answer to check.

Answer: Coordinated commit across systems.

The best option here is Coordinated commit across systems.. Heavy; rarely used in modern ETL. That is exactly the concept behind what is the primary purpose of two-phase commit in this context. The other options are either incomplete or contextually incorrect.

Q39. Which statement about two-phase commit is most accurate?

A. Coordinated commit across systems. B. Single-system commit. C. Pure best-effort. D. Random commits.

Select an answer to check.

Answer: Coordinated commit across systems.

For this question, Coordinated commit across systems. is correct. Heavy; rarely used in modern ETL. That is exactly the concept behind which statement about two-phase commit is most accurate in this context. The other options are either incomplete or contextually incorrect.

Q40. How is two-phase commit best characterized?

A. Random commits. B. Single-system commit. C. Coordinated commit across systems. D. Pure best-effort.

Select an answer to check.

Answer: Coordinated commit across systems.

Coordinated commit across systems. is the correct answer here. Heavy; rarely used in modern ETL. That is exactly the concept behind how is two-phase commit best characterized in this context. The other options are either incomplete or contextually incorrect.

Q41. Which option best describes outbox pattern?

A. Pure cache writes. B. Direct dual-writes. C. Write event to local table + publish. D. Pure best-effort.

Select an answer to check.

Answer: Write event to local table + publish.

Here, Write event to local table + publish. is the right choice. Avoids dual-write inconsistency. It fits the requirement in the prompt about which option best describes outbox pattern. The other options are either incomplete or contextually incorrect.

Q42. What is the primary purpose of outbox pattern?

A. Pure cache writes. B. Pure best-effort. C. Write event to local table + publish. D. Direct dual-writes.

Select an answer to check.

Answer: Write event to local table + publish.

In this case, Write event to local table + publish. is correct. Avoids dual-write inconsistency. It fits the requirement in the prompt about what is the primary purpose of outbox pattern. The other options are either incomplete or contextually incorrect.

Q43. Which statement about outbox pattern is most accurate?

A. Write event to local table + publish. B. Pure best-effort. C. Direct dual-writes. D. Pure cache writes.

Select an answer to check.

Answer: Write event to local table + publish.

The best option here is Write event to local table + publish.. Avoids dual-write inconsistency. It fits the requirement in the prompt about which statement about outbox pattern is most accurate. The other options are either incomplete or contextually incorrect.

Q44. How is outbox pattern best characterized?

A. Pure cache writes. B. Pure best-effort. C. Write event to local table + publish. D. Direct dual-writes.

Select an answer to check.

Answer: Write event to local table + publish.

For this question, Write event to local table + publish. is correct. Avoids dual-write inconsistency. It fits the requirement in the prompt about how is outbox pattern best characterized. The other options are either incomplete or contextually incorrect.

Q45. Which option best describes inbox pattern?

A. Pure outbox only. B. Dedup incoming events on consumer side. C. Pure cache only. D. No dedup at consumer.

Select an answer to check.

Answer: Dedup incoming events on consumer side.

Dedup incoming events on consumer side. is the correct answer here. Pair with at-least-once. It fits the requirement in the prompt about which option best describes inbox pattern. The other options are either incomplete or contextually incorrect.

Q46. What is the primary purpose of inbox pattern?

A. Pure outbox only. B. Dedup incoming events on consumer side. C. Pure cache only. D. No dedup at consumer.

Select an answer to check.

Answer: Dedup incoming events on consumer side.

Here, Dedup incoming events on consumer side. is the right choice. Pair with at-least-once. This is the most accurate statement for what is the primary purpose of inbox pattern. The other options are either incomplete or contextually incorrect.

Q47. Which statement about inbox pattern is most accurate?

A. Pure outbox only. B. Dedup incoming events on consumer side. C. Pure cache only. D. No dedup at consumer.

Select an answer to check.

Answer: Dedup incoming events on consumer side.

In this case, Dedup incoming events on consumer side. is correct. Pair with at-least-once. This is the most accurate statement for which statement about inbox pattern is most accurate. The other options are either incomplete or contextually incorrect.

Q48. How is inbox pattern best characterized?

A. No dedup at consumer. B. Pure outbox only. C. Pure cache only. D. Dedup incoming events on consumer side.

Select an answer to check.

Answer: Dedup incoming events on consumer side.

The best option here is Dedup incoming events on consumer side.. Pair with at-least-once. This is the most accurate statement for how is inbox pattern best characterized. The other options are either incomplete or contextually incorrect.

Q49. Which option best describes checkpointing?

A. Persist progress to skip redo work. B. Restart from scratch always. C. Pure backups only. D. Pure logs only.

Select an answer to check.

Answer: Persist progress to skip redo work.

For this question, Persist progress to skip redo work. is correct. Speeds retries. This is the most accurate statement for which option best describes checkpointing. The other options are either incomplete or contextually incorrect.

Q50. What is the primary purpose of checkpointing?

A. Pure logs only. B. Pure backups only. C. Persist progress to skip redo work. D. Restart from scratch always.

Select an answer to check.

Answer: Persist progress to skip redo work.

Persist progress to skip redo work. is the correct answer here. Speeds retries. This is the most accurate statement for what is the primary purpose of checkpointing. The other options are either incomplete or contextually incorrect.