C100DBA Sharding Practice Question
Which THREE components are required to form a functional MongoDB sharded cluster?
⚠ Common exam trap
Candidates often mistakenly list 'arbiter nodes' or 'primary nodes' as required components, confusing the architectural requirements of a sharded cluster with those of a standard replica set.
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
✓
One or more shards to store the data.
A MongoDB sharded cluster consists of three main components: Shards, Config Servers, and Query Routers (mongos). Shards store the actual data, Config Servers store the cluster's metadata and configuration, and Query Routers act as an interface for applications, directing requests to the appropriate shards. Each plays a distinct and vital role in the cluster's operation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
One or more shards to store the data.
Why this is correct
Shards are the physical servers or replica sets that contain the subset of the sharded data. They provide the actual storage and processing power for the dataset. In a production environment, each shard is implemented as a replica set to ensure high availability and data redundancy.
- ✓
A replica set of config servers.
Why this is correct
Config servers maintain the metadata for the cluster, including the mapping of chunks to shards. Since version 3.4, config servers must be deployed as a replica set. This metadata is essential for the mongos instances to know where to route queries and for the balancer to manage data.
- ✓
One or more mongos query routers.
Why this is correct
The mongos instances act as the entry point for application requests. They do not store data but instead use the metadata from config servers to route reads and writes to the correct shards. Applications connect to mongos just as they would to a standalone mongod or replica set.
- ✗
A dedicated arbiter node for each shard.
Why it's wrong here
Arbiters are optional components in a replica set that participate in elections but do not store data. While they can be used within the replica sets that make up a shard, they are not a required component of the sharding architecture itself and are generally discouraged in production environments.
- ✗
A central MongoDB Ops Manager instance.
Why it's wrong here
Ops Manager is a management platform for automation, monitoring, and backup of MongoDB deployments. While highly recommended for managing complex sharded clusters, it is an auxiliary tool and not a technical requirement for the cluster itself to function and process data requests from an application.
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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.