C100DBA Replication Practice Question
In a three-node replica set with default write concerns, what occurs when the primary node experiences a network partition and cannot communicate with the majority of the set?
⚠ Common exam trap
Candidates often assume the partitioned primary continues accepting writes, forgetting that the lack of a network majority forces it to step down.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The primary steps down to secondary status, and the set elects a new primary.
When a primary loses connectivity to the majority of the replica set, it steps down to secondary status to prevent split-brain scenarios. This process ensures data consistency by requiring a majority of nodes to acknowledge writes. The remaining nodes will initiate an election to choose a new primary, maintaining the availability and integrity of the cluster during the temporary partition event.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The primary continues accepting writes until the partition is resolved.
Why it's wrong here
A primary node that cannot reach a majority of its voting members will automatically step down to secondary status. This behavior is a core safety mechanism in MongoDB to prevent stale reads and inconsistent writes in the event of a network failure or a total loss of cluster quorum.
- ✗
The primary immediately crashes and shuts down the mongod process.
Why it's wrong here
MongoDB does not shut down the mongod process when a partition occurs. Instead, it transitions the primary into a secondary state where it can no longer accept writes, preserving the existing data and allowing it to catch up on replication logs once network connectivity is restored to the set.
- ✓
The primary steps down to secondary status, and the set elects a new primary.
Why this is correct
When a primary node detects that it can no longer see a majority of the voting members, it transitions to a secondary state. This is essential for cluster health because it allows the remaining nodes in the replica set to hold an election and select a new primary to handle operations.
- ✗
The secondary nodes force a rollback on the primary node.
Why it's wrong here
Rollbacks only occur when a former primary rejoins the set and must revert uncommitted operations to match the current majority-confirmed data. The primary node stepping down during a partition is a graceful state transition, not an automatic rollback process, as the existing primary was simply unable to reach majority consensus.
About these practice questions
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official MongoDB exam blueprint
This C100DBA practice question is part of Courseiva's free MongoDB certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the C100DBA exam.