C100DEV Drivers, Tools, Transactions, and Search Practice Question
A developer needs to create an Atlas Search index that supports autocomplete on a `name` field. Which Atlas Search index definition is required?
⚠ Common exam trap
Candidates often confuse MongoDB text indexes with Atlas Search autocomplete field types, which serve different purposes.
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
✓
An index with a field of type 'autocomplete' and an analyzer such as 'lucene.standard' or a custom edge-gram analyzer.
Atlas Search uses the `autocomplete` field type to support prefix suggestions. The field must be configured with an analyzer that produces edge-grams or n-grams, such as a custom analyzer using the edgeGram tokenizer. Standard string or text indexes do not provide this behavior. Wildcard indexes are unrelated to Atlas Search and cannot satisfy the autocomplete requirement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
A text index with the default language analyzer.
Why it's wrong here
A text index supports word-based search and stemming, but not prefix autocomplete. It does not generate edge-grams for partial matches. It fails here because the requirement is autocomplete, which needs the Atlas Search autocomplete type and an appropriate analyzer.
- ✗
A standard string index with dynamic mapping enabled.
Why it's wrong here
Dynamic mapping indexes fields automatically as strings, but it does not create the special edge-gram or nGram analyzers needed for autocomplete. A standard string index supports full-text search, not prefix-based suggestions. It fails here because autocomplete requires a dedicated type with a specific analyzer.
- ✓
An index with a field of type 'autocomplete' and an analyzer such as 'lucene.standard' or a custom edge-gram analyzer.
Why this is correct
Atlas Search provides the `autocomplete` field type specifically for prefix-based suggestions. It requires an analyzer that generates edge-grams or n-grams, such as `lucene.standard` with edgeGram or a custom analyzer. This matches the scenario because the developer needs autocomplete on the `name` field.
- ✗
A wildcard index on the `name` field.
Why it's wrong here
Wildcard indexes are a MongoDB core feature for flexible document fields, not an Atlas Search index type. They do not provide text analyzers or prefix search. It fails here because Atlas Search autocomplete requires the autocomplete field type, not a wildcard index.
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.