C100DBA Sharding Practice Question
Exhibit
{
"ns": "finance.accounts",
"min": { "region": "EMEA", "account_id": MinKey },
"max": { "region": "EMEA", "account_id": MaxKey },
"shard": "shard01"
}Refer to the exhibit. An administrator inspects chunk metadata for a sharded collection using a compound shard key: { region: 1, account_id: 1 }. What does the presence of MinKey and MaxKey signify in this specific chunk range definition?
⚠ Common exam trap
Candidates often misinterpret MinKey and MaxKey as actual data values within the document, rather than understanding them as internal BSON boundary markers used for chunk range definitions.
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
✓
They represent absolute lower and upper bounds for the account_id field within the EMEA region, ensuring all accounts for that region reside in this chunk.
MinKey and MaxKey represent lower and upper boundary markers in MongoDB that evaluate smaller or larger than any other BSON data type. In this compound chunk range, they ensure that all documents matching the 'EMEA' region regardless of their account_id value fall within this specific chunk. Understanding BSON boundary types is essential for troubleshooting custom chunk splits and zone sharding configurations.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
They represent absolute lower and upper bounds for the account_id field within the EMEA region, ensuring all accounts for that region reside in this chunk.
Why this is correct
They represent absolute lower and upper bounds for the account_id field within the EMEA region, ensuring all accounts for that region reside in this chunk. MinKey and MaxKey act as universal wildcards for the trailing compound fields, capturing all possible account identifiers associated with the EMEA region inside shard01.
- ✗
They indicate that the chunk is corrupted and requires immediate repair using the validate command on the config server.
Why it's wrong here
They indicate that the chunk is corrupted and requires immediate repair using the validate command on the config server. MinKey and MaxKey are standard internal BSON types utilized by MongoDB to define open-ended or bounded compound chunk ranges without indicating any form of data corruption.
- ✗
They specify encryption keys used by the WiredTiger storage engine to secure data chunks at rest on shard01.
Why it's wrong here
They specify encryption keys used by the WiredTiger storage engine to secure data chunks at rest on shard01. Storage encryption keys are managed separately through KMIP or local key files and have no relationship to chunk boundary definitions or BSON range keys.
- ✗
They are temporary placeholder values assigned by the balancer during active chunk splits that will automatically expire after twenty-four hours.
Why it's wrong here
They are temporary placeholder values assigned by the balancer during active chunk splits that will automatically expire after twenty-four hours. MinKey and MaxKey remain permanently embedded as boundary markers in chunk metadata to define valid sort and range limits indefinitely.
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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 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.