C100DEV Data Modeling Practice Question
What happens if a document grows beyond the 16MB limit due to an 'Embedding' design choice?
⚠ Common exam trap
Many students think MongoDB automatically truncates oversized data or splits documents across pages, forgetting that the 16MB limit is a strict rule causing total write failure.
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 write operation will fail.
When a document exceeds 16MB, the MongoDB write operation fails, and the database returns an error. The BSON document size limit is a hard constraint in MongoDB. This scenario highlights why 'unbounded array' design patterns must be avoided. When designing schemas, developers must ensure that embedded data sets have a predictable upper bound, or they must switch to a referencing strategy to maintain the integrity of their data storage.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
MongoDB automatically moves the overflow data to a new document.
Why it's wrong here
MongoDB does not automatically move data between documents. If a write operation would push a document over 16MB, the entire write fails. The application is responsible for managing document size and ensuring that the schema is designed to prevent documents from reaching the hard limit defined by the BSON specification.
- ✓
The write operation will fail.
Why this is correct
The 16MB limit is a hard architectural constraint. If an update causes a document to exceed this size, the database rejects the change and returns an error. This is why careful schema modeling, such as using the Subset pattern or Referencing, is essential for datasets that grow over time.
- ✗
The engine automatically compresses the document to fit.
Why it's wrong here
While WiredTiger uses compression for disk storage, the BSON limit applies to the uncompressed document in memory. Compression is a storage-level feature that does not allow you to bypass the 16MB limit, which is defined at the logical document level, not the physical disk storage level. You cannot exceed this limit.
- ✗
The document is split into two, and the original ID is shared.
Why it's wrong here
MongoDB does not have a native 'split' mechanism for documents. Every document must have a unique _id. If you need to break up data, you must implement the application logic to move data to a separate collection or a different document structure; the database will not do this for you.
About these practice questions
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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.