300+ MongoDB Interview Questions Practice Test

1. C

The term ‘sharding’ in MongoDB refers to the process of distributing data across multiple servers or shards. Sharding is a form of horizontal scaling that allows MongoDB databases to scale out and handle more data and more queries than a single server could manage. Each shard holds a portion of the data and functions as a separate database, which allows for efficient management of large datasets and high throughput operations.
2. C
The primary purpose of using an index in MongoDB is to improve the efficiency of data retrieval operations. Indexes enable quick lookups by storing a small portion of the collection’s data in a form that can be traversed efficiently. Without indexes, MongoDB would have to perform full collection scans to satisfy queries, which can be very slow on large datasets.
3. C
The ‘Write Concern’ setting in MongoDB dictates the level of acknowledgment required from MongoDB for write operations. It is a critical configuration that ensures data durability and consistency, and it can be set to various levels depending on the required guarantees of data being written successfully. For example, writing to a majority of nodes in a replica set provides higher durability at the cost of lower write performance.
4. B
The oplog (operations log) is a core component of MongoDB’s replication mechanism. It is a capped collection that records every operation performed by the primary node. Secondary nodes then use the oplog to replicate and apply these operations, ensuring that all members of a replica set remain in sync with each other.
5. C
GridFS is a specification in MongoDB for storing and retrieving large files that exceed the BSON-document size limit of 16MB. It works by splitting the file into smaller chunks and storing each chunk as a separate document. GridFS enables efficient management of large files, allowing users to store, retrieve, and update them in a manner similar to how they work with standard MongoDB documents.
The explanations provided are accurate based on the options given for each question. The sample questions cover key concepts in MongoDB such as sharding, indexing, write concern, oplog, and GridFS. These concepts are essential for anyone looking to master MongoDB and understand its capabilities and best practices.