C100DBA Philosophy and Features Practice Question
What is the primary motivation for MongoDB's 'WiredTiger' storage engine to provide document-level concurrency control?
⚠ Common exam trap
Candidates often confuse document-level concurrency with transaction isolation, failing to realize the primary goal of document-level locking is to eliminate write contention and increase global throughput.
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
✓
To increase throughput by reducing write contention.
Early MongoDB versions used a global write lock, which hindered performance by serializing all write requests. Document-level concurrency control allows multiple clients to write to different documents in the same collection simultaneously. This is a critical architectural shift that enables high write throughput, as it drastically reduces contention and allows the database to fully utilize multi-core server architectures, directly supporting MongoDB's promise of high performance at scale.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
To allow for faster reading of large binary objects.
Why it's wrong here
Document-level locking is focused on write contention, not read optimization. While it improves overall system performance, its specific role is to enable simultaneous writes to different documents, rather than changing how the engine reads and interprets large binary data structures stored in the database.
- ✗
To support atomic, multi-document transactions.
Why it's wrong here
While document-level concurrency control is a prerequisite for robust transactional systems, the primary goal is reducing write contention. Transactions are a higher-level feature built on top of this locking mechanism, which enables fine-grained control over which data is modified during concurrent operations.
- ✓
To increase throughput by reducing write contention.
Why this is correct
Document-level concurrency control minimizes the lock scope, allowing independent writes to proceed in parallel. This significantly increases system throughput, as the database can handle numerous concurrent write requests without forcing them into a single, serialized queue that would otherwise limit performance on high-end hardware.
- ✗
To provide automatic index creation in the background.
Why it's wrong here
Background index creation is a task management feature. While it uses the engine's capabilities, it is distinct from concurrency control. Concurrency control manages how data updates are handled at the document level, whereas indexing is a separate process that manages how data is searched and retrieved.
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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.