C100DBA Replication Practice Question
You are configuring a MongoDB replica set for a global application. You need to add a member that will never become primary and will be invisible to client applications. Which two steps must you take when adding this member? (Choose two.)
⚠ Common exam trap
The trap here is thinking that setting votes to 0 or slaveDelay is sufficient to make a member non-primary and hidden, when actually hidden and priority 0 are the required settings.
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
✓
Set its priority to 0.
To create a member that never becomes primary and is invisible to clients, you must set both priority to 0 and hidden to true. Priority 0 ensures it cannot be elected primary, while hidden true prevents client visibility and use as a sync source. These two settings together meet the requirements.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Set its votes to 0.
Why it's wrong here
Setting votes to 0 makes the member non-voting in elections, but it does not prevent it from becoming primary if it has a non-zero priority and is not hidden. Also, a non-voting member can still be visible to clients. This setting is not required for a hidden member.
- ✗
Set its slaveDelay to a large value.
Why it's wrong here
slaveDelay (now called secondaryDelaySecs) delays replication, but it does not affect visibility to clients or prevent the member from becoming primary. A delayed member can still be elected primary if its priority is greater than 0 and it is not hidden. This setting is unrelated to the requirements.
- ✓
Set its priority to 0.
Why this is correct
Setting priority to 0 prevents the member from being elected primary. However, it alone does not make the member invisible to clients. A priority 0 member can still be a sync source and can serve reads if clients connect with appropriate read preferences, unless it is also hidden.
- ✗
Set its buildIndexes to false.
Why it's wrong here
buildIndexes false prevents the member from building non-_id indexes, which is useful for reducing overhead. However, it does not affect visibility or election eligibility. A member with buildIndexes false can still become primary if priority > 0 and not hidden. This setting is not required here.
- ✓
Set its hidden property to true.
Why this is correct
Setting hidden to true prevents the member from being visible to client applications and from being a sync source for other secondaries. However, hidden members must also have priority 0 to ensure they cannot become primary. Both settings are required to meet the requirements.
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.