C100DEV Aggregation Framework Practice Question
What happens if an aggregation stage exceeds the 100MB memory limit and 'allowDiskUse' is set to false?
⚠ Common exam trap
Candidates often assume that MongoDB will automatically spill to disk when memory is exceeded, forgetting that allowDiskUse must be explicitly set to true to enable this 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 aggregation operation fails and returns an error.
By default, MongoDB limits each aggregation stage to 100MB of RAM to prevent a single query from consuming excessive system resources and affecting database stability. If a stage exceeds this limit without explicit permission to write to temporary files on disk, the query will fail with an error. Developers must proactively optimize pipelines to minimize memory footprint or enable disk use when large-scale processing is required.
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 pipeline execution stalls until memory is freed.
Why it's wrong here
The MongoDB aggregation framework does not wait for memory to free up; it terminates the operation immediately to protect the server. Stalling would lead to thread starvation and system instability, which is precisely why the error-out behavior is enforced as a safety mechanism.
- ✗
The database automatically increases the limit.
Why it's wrong here
MongoDB does not dynamically adjust resource limits based on query requirements. The 100MB limit is a fixed safeguard to ensure that queries do not consume all available system RAM, which would cause an Out-Of-Memory (OOM) event that could crash the entire MongoDB process.
- ✓
The aggregation operation fails and returns an error.
Why this is correct
When memory usage exceeds 100MB and allowDiskUse is false, the database throws an error to prevent resource exhaustion. This forces developers to design more efficient pipelines or intentionally enable disk usage, ensuring that resource-heavy queries are executed with full awareness of the potential performance trade-offs.
- ✗
The pipeline skips the stage and continues.
Why it's wrong here
Skipping a stage would lead to inaccurate results, which is unacceptable for database operations. The engine strictly requires each stage to complete successfully. If a stage cannot process its data within the allocated constraints, the only safe action is to halt execution entirely.
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.