C100DBA Application Administration Practice Question
An application is performing many updates to a document. Which strategy is most effective to avoid fragmentation in the data files?
⚠ Common exam trap
Candidates frequently suggest defragmentation utilities similar to traditional relational databases, ignoring that MongoDB requires document padding or schema redesign to prevent movement overhead.
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
✓
Add padding to the documents to accommodate future growth.
Document growth is a primary cause of fragmentation in MongoDB collections. When a document grows and no longer fits in its current location on disk, it must be moved to a new location. By pre-allocating space or using an embedding strategy that keeps documents within a predictable size range, administrators can reduce the frequency of document moves, thereby minimizing disk fragmentation and maintaining long-term database performance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use the 'compact' command during peak traffic hours.
Why it's wrong here
The compact command is resource-intensive and blocks operations, which is extremely detrimental during peak traffic. Running it then would cause significant performance degradation for the application. Compaction should only be performed during maintenance windows when the database load is minimal or non-existent.
- ✓
Add padding to the documents to accommodate future growth.
Why this is correct
Adding padding (extra space) to a document ensures that it has room to grow without needing to be relocated on disk. This significantly reduces fragmentation in the data files caused by document moves, which is a key requirement for maintaining high update performance in MongoDB collections.
- ✗
Disable the WiredTiger cache periodically.
Why it's wrong here
Disabling the cache is not a valid administrative action and would lead to extreme performance loss. The cache is essential for the function of the WiredTiger engine, and turning it off does nothing to address fragmentation, which is a disk-level issue unrelated to RAM.
- ✗
Perform a collection scan after every update.
Why it's wrong here
Performing a collection scan is a read operation that consumes significant CPU and I/O resources. It has no effect on data file fragmentation or document storage patterns. This suggestion is unrelated to solving fragmentation and would drastically slow down the application's performance.
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.