C100DBA Application Administration Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  { w: 1, j: true }

  Why it's wrong here

  This write concern requires acknowledgment from only the primary (w: 1) but does require journaling. While it ensures the write is journaled on the primary, it does not wait for a majority of members to acknowledge. If the primary fails before replicating, the write could be lost. Thus, it does not satisfy the majority acknowledgment requirement.

• ✗

  { w: "majority", j: false, wtimeout: 5000 }

  Why it's wrong here

  This write concern requires majority acknowledgment but no journaling, and adds a timeout. The timeout means that if the write is not acknowledged by a majority within 5000 ms, it returns an error. However, the lack of journaling means the write may not be persisted to disk. This does not meet the journaling requirement.

• ✓

  { w: "majority", j: true }

  Why this is correct

  This write concern requires acknowledgment from a majority of voting members (w: "majority") and also requires that the write be written to the on-disk journal (j: true) before returning success. This matches the requirement exactly: majority acknowledgment plus journaling. It provides strong durability and is suitable for critical data.

• ✗

  { w: "majority", j: false }

  Why it's wrong here

  This write concern requires majority acknowledgment but does not require journaling. While it ensures that the write is replicated to a majority of members, it does not guarantee that the write is persisted to disk on those members. A power failure could still lose the write if it was not journaled. Therefore, it does not meet the requirement of journaling before acknowledgment.