C100DBA Philosophy and Features Practice Question
A financial services company is evaluating MongoDB for a new application that requires strong consistency for critical transactions and high availability across multiple data centers. The team must choose features that align with MongoDB's philosophy of balancing consistency, availability, and partition tolerance. (Choose two.)
⚠ Common exam trap
The trap here is assuming that high availability always means using the nearest read preference, which sacrifices consistency.
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
✓
Read concern "majority"
Read concern "majority" and write concern "majority" together provide strong consistency and durability by ensuring that reads and writes are acknowledged by a majority of replica set members. This combination is essential for critical financial transactions that cannot tolerate stale reads or data loss. These features reflect MongoDB's tunable consistency model, allowing the company to balance consistency and availability according to their 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.
- ✗
Write concern "w: 1"
Why it's wrong here
Write concern "w: 1" acknowledges a write after it is written to the primary only. While this provides low latency, it does not ensure durability across multiple data centers and can lead to data loss if the primary fails before replication. For critical financial transactions requiring strong consistency and high availability, this write concern is insufficient and does not align with the company's requirements.
- ✗
Read preference "nearest"
Why it's wrong here
Read preference "nearest" directs reads to the replica set member with the lowest network latency, which can improve performance but does not guarantee strong consistency. It may return stale data if the nearest member is a secondary that has not yet replicated the latest writes. This option contradicts the need for strong consistency in critical transactions, making it unsuitable for the scenario.
- ✓
Read concern "majority"
Why this is correct
Read concern "majority" ensures that data read has been acknowledged by a majority of replica set members, providing stronger consistency guarantees. This aligns with the need for strong consistency in critical transactions, as it prevents reading uncommitted or rolled-back data. It is a key feature for applications that cannot tolerate stale reads, and it reflects MongoDB's tunable consistency model.
- ✓
Write concern "majority"
Why this is correct
Write concern "majority" requires that a write is acknowledged by a majority of replica set members before returning success. This ensures durability and consistency across data centers, as the write is persisted on multiple nodes. It is essential for critical transactions where data loss is unacceptable, and it directly supports the company's requirement for strong consistency and high availability.
- ✗
Read concern "local"
Why it's wrong here
Read concern "local" returns data from the instance without guaranteeing that it has been replicated to a majority of members. It can expose uncommitted or rolled-back data, which is unacceptable for critical transactions. This option prioritizes performance over consistency and is not suitable for the financial services scenario that demands strong consistency and reliability across data centers.
About these practice questions
Courseiva writes every C100DBA question from scratch — 222 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or 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.