C100DBA Application Administration Practice Question
Which connection string parameter should be used to ensure that an application only reads data from nodes that are considered current and consistent?
⚠ Common exam trap
Candidates often confuse 'primary' read preference with 'nearest' or 'primaryPreferred', failing to realize that 'primary' is the only setting that guarantees reading the most current 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
✓
readPreference=primary
Read preference settings dictate where the application directs its read operations. Using 'primary' ensures that the application always reads the most recent data, avoiding the latency issues inherent in replication lag. This is critical for applications that require strong consistency and cannot tolerate reading stale data, such as financial transactions or inventory management systems, where data accuracy is paramount.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
readPreference=secondary
Why it's wrong here
Secondary read preference allows reading from secondary nodes, which may have data that is behind the primary due to replication lag. This introduces the risk of reading stale data, which is unacceptable for applications requiring strong consistency and immediate data accuracy.
- ✓
readPreference=primary
Why this is correct
Primary read preference forces all operations to go to the primary node, which is the source of truth for all writes. This guarantees the application reads the most recent, consistent data, preventing the issues associated with replication lag that occur when reading from secondary members.
- ✗
readPreference=nearest
Why it's wrong here
Nearest read preference directs operations to the node with the lowest network latency, which could be a secondary node. This provides no guarantee regarding data freshness and is generally unsuitable for applications that require strict consistency for their business operations.
- ✗
readPreference=secondaryPreferred
Why it's wrong here
Secondary preferred reads from a secondary member if one is available, otherwise it falls back to the primary. This configuration still allows for stale reads if a secondary is chosen, making it inappropriate for applications requiring strong consistency and current data at all times.
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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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