C100DBA Replication Practice Question
What is the primary purpose of an Arbiter in a MongoDB replica set?
⚠ Common exam trap
Candidates often assume arbiters hold backup copies of data for failover scenarios, confusing them with standard secondary nodes.
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
✓
To participate in elections and help achieve a majority.
An arbiter's sole purpose is to participate in elections to help reach a majority vote without storing any data. By not storing data, it remains lightweight and requires minimal hardware resources, providing a cost-effective way to fulfill the voting requirements of a replica set in scenarios where an extra full-data node is not needed for capacity or redundancy.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
To serve as a standby node for automatic failover.
Why it's wrong here
Arbiters cannot become primary nodes because they do not contain any data. They do not act as standby nodes for failover in the sense of taking over write traffic; they only exist to contribute a vote during an election, helping the set reach the required majority to elect a primary.
- ✓
To participate in elections and help achieve a majority.
Why this is correct
The arbiter exists strictly to vote in elections. In a replica set, elections require a majority of voting members to succeed. By adding an arbiter, you increase the number of voting members, which can help reach that majority quorum without the cost or storage requirements of a full-data node.
- ✗
To provide read-only access to the database.
Why it's wrong here
Arbiters do not store data, so they cannot serve read requests. Any attempt by a client driver to route read operations to an arbiter will fail because there is no collection data for the arbiter to query, making it strictly a voting participant in the replica set infrastructure.
- ✗
To replicate data from the primary to secondary nodes.
Why it's wrong here
Arbiters are not part of the data replication stream. They do not receive or store oplog entries. The replication process happens between the primary and the data-bearing secondary nodes. The arbiter is strictly involved in the cluster's membership and health-management logic, specifically regarding the election of a new primary node.
About these practice questions
This C100DBA question is part of Courseiva's 222-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
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.