C100DBA Sharding Practice Question
A sharded cluster has a three-member replica set for its config servers. If two of the three config servers go offline, what is the immediate impact on the cluster's operations?
⚠ Common exam trap
Candidates often think losing config server quorum completely stops all read and write operations on existing sharded data.
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
✓
Chunks cannot be split or migrated between shards.
Config servers store the metadata and configuration settings for the entire sharded cluster. They are deployed as a replica set to ensure high availability. If the replica set loses its majority, it can no longer process writes to the metadata, which has significant implications for administrative tasks and the dynamic behavior of the cluster.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The cluster becomes read-only for all application data.
Why it's wrong here
The loss of config server majority only affects the cluster's metadata. Application data stored on the shards remains accessible for both reads and writes. As long as the shards themselves are healthy and the mongos instances have cached the necessary routing information, the application can continue to function normally.
- ✗
The mongos instances will crash and must be restarted.
Why it's wrong here
Mongos instances are designed to be resilient. They cache routing metadata locally. While they will be unable to refresh this cache if the config servers are unavailable, they do not crash. They will continue to route requests based on their existing cache until the config servers return to service.
- ✓
Chunks cannot be split or migrated between shards.
Why this is correct
Operations that require updating the cluster metadata, such as chunk splits, migrations, or dropping collections, will fail because the config server replica set lacks a majority to commit writes. The cluster remains operational for standard data access, but its ability to balance or scale is temporarily frozen.
- ✗
All shards will automatically step down their primary members.
Why it's wrong here
The health of the shard replica sets is independent of the config server replica set. Shards use their own internal heartbeats and elections to maintain a primary. The loss of config server availability does not trigger any changes to the leadership or state of the individual shard replica sets.
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.