C100DBA Sharding Practice Question
A MongoDB 6.0 sharded cluster has a collection with a ranged shard key on the field 'customerId'. The balancer has been running normally, but the operations team notices that one shard consistently holds significantly more chunks than the others. They want to understand which internal metadata collection the mongos uses to determine chunk distribution and to verify the current chunk-to-shard mapping. Which collection should they query?
⚠ Common exam trap
The trap here is assuming that config.shards contains chunk distribution details, when it only lists shard hosts and states.
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
✓
config.chunks
Chunk distribution is tracked in the config database, specifically in config.chunks, which maps each chunk's key range to its host shard. To verify which shard holds more chunks, an administrator queries config.chunks. The other collections store different metadata: shard list, collection definitions, or version info, none of which include per-chunk placement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
config.shards
Why it's wrong here
config.shards lists the shards in the cluster and their host connection strings, but it does not contain chunk-to-shard mappings. It is useful for verifying shard membership and state, but it cannot show which shard holds which key ranges, so it would not answer the question about uneven chunk distribution.
- ✗
config.collections
Why it's wrong here
config.collections stores metadata about sharded collections, such as the namespace, shard key pattern, and unique flag. It does not record individual chunk locations or counts per shard. While it confirms that a collection is sharded and its key pattern, it cannot reveal why one shard has more chunks.
- ✗
admin.system.version
Why it's wrong here
admin.system.version holds the cluster's feature compatibility version and other internal versioning information. It has no relation to chunk distribution or shard key ranges. Querying it would not show chunk ownership, so it is irrelevant to diagnosing an imbalanced chunk count across shards.
- ✓
config.chunks
Why this is correct
The config.chunks collection in the config database stores the mapping of each chunk to its shard, including the min and max shard key values. Querying config.chunks on a mongos or config server replica set member reveals the exact chunk distribution, allowing the team to confirm which shard owns which ranges and to diagnose imbalance.
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.