C100DEV Drivers, Tools, Transactions, and Search Practice Question
In the context of the MongoDB Node.js driver, what happens if an application fails to provide a write concern?
⚠ Common exam trap
Candidates often incorrectly assume that omitting a write concern will cause the operation to fail or wait for all replicas, rather than defaulting to the standard 'w: 1' behavior.
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
✓
The driver applies the default write concern (usually 'w: 1').
If no write concern is explicitly defined, the driver uses the default write concern configured at the client or database level. If no default is configured, the driver falls back to 'w: 1', meaning the operation is considered successful once the primary node receives and acknowledges the write. This is the standard behavior to balance performance with a baseline level of data durability in most production applications.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The write will never be acknowledged by the server.
Why it's wrong here
Operations always require some form of acknowledgement to confirm they reached the server, unless explicitly configured otherwise. If no write concern is provided, the driver applies the default, which ensures that the primary node acknowledges the write, preventing the application from proceeding without knowing the operation was received.
- ✗
The server automatically sets the write concern to 'majority'.
Why it's wrong here
The server does not automatically escalate to 'majority' because this would significantly increase latency and resource usage for all operations. The default is typically 'w: 1', which provides the fastest response time, assuming that a single node failure risk is acceptable for most standard, non-transactional database operations.
- ✓
The driver applies the default write concern (usually 'w: 1').
Why this is correct
By default, the MongoDB driver uses a write concern of 'w: 1'. This ensures the primary node writes the data to its journal or memory and acknowledges the request. This provides a balance between performance and immediate confirmation, suitable for general-purpose applications that do not require maximum consistency guarantees.
- ✗
The write will be rejected by the MongoDB server.
Why it's wrong here
The MongoDB server will not reject a write simply because the client did not specify a write concern. It will simply apply the default level of acknowledgement configured on the server. If the client does not specify it, the driver provides the default, ensuring the operation proceeds normally.
About these practice questions
This C100DEV question is part of Courseiva's 259-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 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.