C100DBA Replication 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.

• ✗

  It guarantees that the read will never return stale data.

  Why it's wrong here

  While 'majority' ensures the data is durable, it does not guarantee that the data is the absolute latest version on the primary. A node could still be slightly behind. For absolute latest data, 'readConcern: linearizable' is required, though it comes with a significant performance penalty for every single read operation.

• ✓

  It guarantees that the data read has been committed to a majority of nodes.

  Why this is correct

  This read concern ensures that the returned data is part of the majority-committed history. This means the data is permanent and cannot be rolled back during a future election. It is a fundamental feature for building reliable distributed systems where data integrity must be maintained across node failures.

• ✗

  It forces the read to always come from the primary node.

  Why it's wrong here

  Read concern majority can be used on secondary nodes as well as the primary. It does not dictate which node handles the read, only that the data being read meets the durability criteria of being confirmed by a majority of the members in the current replica set cluster configuration.

• ✗

  It increases the speed of queries by ignoring consistency.

  Why it's wrong here

  Quite the opposite, majority read concern can introduce additional latency because it must verify the data's durability with other replica set members. It prioritizes consistency and durability over raw performance. Applications that prioritize speed over consistency would typically use 'readConcern: local' instead, which provides the most recent data available locally.