C100DEV Drivers, Tools, Transactions, and Search Practice Question
Which of the following describes the behavior of a 'causally consistent' session in MongoDB?
⚠ Common exam trap
Candidates often confuse causal consistency with 'strong consistency' or 'read-your-writes' across all nodes. They fail to realize it is specific to the logical order within a session.
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
✓
It ensures operations are observed in their logical order.
Causal consistency ensures that operations within a session reflect the order in which they were performed. If an application writes a document and then immediately reads it back within the same session, causal consistency guarantees that the read will see the result of that write, even if the read is directed to a secondary node. This is vital for applications requiring linear-like history for user interactions across distributed read/write nodes.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
It forces all reads and writes to the primary node.
Why it's wrong here
Causal consistency does not require the primary node; it uses client-side operation times to ensure that reads are consistent with preceding writes, even when directed to secondary nodes. This allows for horizontal read scaling without sacrificing the perception of consistency that the application expects during a user session.
- ✓
It ensures operations are observed in their logical order.
Why this is correct
Causal consistency guarantees that the database reflects the logical order of operations performed within the session. It ensures that 'read-your-writes' is respected across the cluster, preventing scenarios where a client might see an outdated version of data that should have already been updated by a previous write.
- ✗
It eliminates the need for replication in the cluster.
Why it's wrong here
Replication remains a requirement for high availability and durability. Causal consistency is a feature that works on top of replication, managing how clients perceive data consistency during read operations. It has no impact on the necessity or functionality of the replication process itself within the MongoDB cluster.
- ✗
It significantly increases the latency of every write.
Why it's wrong here
Causal consistency is handled by passing operation tokens (timestamps) between the client and server. This adds very minimal overhead and does not significantly impact write latency. The benefit of consistent reads across the replica set far outweighs the negligible cost of tracking these operation times for the session.
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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 C100DEV 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 C100DEV exam.