C100DBA Application Administration Practice Question
An application uses a time-series collection. What is the benefit of using the TTL (Time-To-Live) index feature?
⚠ Common exam trap
Candidates often think TTL indexes are used for query performance optimization, when their primary purpose is strictly data lifecycle management and automated record deletion.
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
✓
It allows the database to remove documents based on a timestamp field.
TTL indexes provide an automated mechanism for cleaning up expired data. By setting a TTL index on a date field, MongoDB periodically removes documents that exceed the defined age, which is essential for managing storage and keeping the database size under control in time-series workloads. This reduces administrative manual cleanup tasks and ensures the system maintains a consistent performance level by pruning old, irrelevant data automatically.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
It automatically creates a new collection for every time period.
Why it's wrong here
TTL indexes operate on existing documents within a collection; they do not trigger collection rotation or partitioning. While they help manage data volume, they are not a substitute for architectural data lifecycle strategies like sharding or collection-per-time-interval, which require manual or custom implementation.
- ✗
It ensures data is compressed automatically to save disk space.
Why it's wrong here
Data compression is managed by the storage engine (WiredTiger), not by indexing. TTL indexes are solely for the removal of expired data based on a timestamp field, and they do not affect the compression ratio or the storage format of the documents.
- ✓
It allows the database to remove documents based on a timestamp field.
Why this is correct
A TTL index enables the background removal of documents after a specified number of seconds. This automates data lifecycle management by deleting expired records based on a date-typed field, keeping the collection size manageable without requiring custom application code or manual deletion scripts.
- ✗
It prevents duplicate documents from being inserted into the collection.
Why it's wrong here
Uniqueness is handled by unique indexes, not TTL indexes. A TTL index only tracks document age to determine deletion eligibility; it does not enforce constraints on field values, meaning it cannot prevent duplicate data insertions, which requires a separate unique index configuration.
About these practice questions
This C100DBA question is part of Courseiva's 222-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 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.