C100DBA Application Administration Practice Question
A database administrator wants to configure a read preference that directs all read operations to the primary node of a replica set, ensuring the most up-to-date data. Which read preference mode should be used?
⚠ Common exam trap
Candidates often confuse "primaryPreferred" with "primary". "primaryPreferred" only reads from the primary when it is available; if the primary is down, it reads from secondaries, which may not have the latest data.
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
✓
primary
The requirement is to always read the most up-to-date data, which is only guaranteed when reading from the primary. The "primary" read preference ensures that all reads are directed to the primary node. Other read preferences may read from secondaries, which can have stale data, or may fall back to secondaries if the primary is unavailable, violating the requirement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
primaryPreferred
Why it's wrong here
"primaryPreferred" reads from the primary if it is available, but falls back to secondaries if the primary is unavailable. While it often reads from the primary, it does not guarantee that all reads go to the primary. If the primary is down, reads go to secondaries, which may have stale data. This does not meet the requirement of always reading from the primary.
- ✓
primary
Why this is correct
The "primary" read preference directs all read operations to the primary node of the replica set. This ensures that the application always reads the most current data, as the primary is the only node that accepts writes. It is the default read preference and is suitable when strong consistency is required.
- ✗
nearest
Why it's wrong here
"nearest" read preference selects the member with the lowest network latency, regardless of whether it is a primary or secondary. This can result in reads from secondaries, which may have stale data. It is designed to minimize latency, not to ensure reading the most current data. Therefore, it does not satisfy the requirement.
- ✗
secondary
Why it's wrong here
"secondary" read preference directs reads to secondary nodes only. This can result in reading stale data because secondaries may lag behind the primary. Since the administrator wants the most up-to-date data, this mode is inappropriate. It is used to offload read traffic from the primary, but at the cost of consistency.
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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
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