Below are 10 Important MongoDB Interview Questions and Answers
1. What is MongoDB?
Answer: MongoDB is a NoSQL database management system that stores data in flexible, JSON-like documents. It is designed to be scalable, flexible, and high-performing, making it suitable for handling large volumes of data in various applications.
2. Explain the key features of MongoDB.
Answer: Some key features of MongoDB include:
- Document-Oriented: Uses JSON-like documents to store data.
- High Performance: Provides high speed and scalability.
- Schema-less: Allows dynamic and flexible schemas.
- Replication and High Availability: Supports replica sets for redundancy and failover.
- Indexing: Offers various indexing options to improve query performance.
- Aggregation Framework: Facilitates data aggregation operations like grouping, filtering, and more.
3. Differentiate between SQL databases and MongoDB.
Answer: SQL databases are relational databases that use tables and rows to store data. MongoDB, on the other hand, is a NoSQL database that stores data in collections of JSON-like documents. MongoDB offers a flexible schema, better scalability, and allows for easier horizontal scaling compared to SQL databases.
4. What is a Replica Set in MongoDB?
Answer: A Replica Set is a group of MongoDB instances that maintain the same data set for redundancy and high availability. It consists of multiple copies of data distributed across different servers. In a Replica Set, one node is the primary node handling all write operations, while others are secondary nodes replicating data from the primary node.
5. Explain Sharding in MongoDB.
Answer: Sharding in MongoDB is a technique used for horizontal scaling of data across multiple machines. It involves distributing data across shards, which are separate instances of MongoDB, to handle large amounts of data. Sharding improves query performance and allows for increased data storage capacity.
6. What is GridFS in MongoDB?
Answer: GridFS is a specification used in MongoDB to store and retrieve files that exceed the BSON document size limit (16 MB). It breaks files into smaller chunks and stores them as separate documents, allowing efficient storage and retrieval of large files.
7. How does indexing work in MongoDB?
Answer: MongoDB uses indexes to facilitate efficient query execution by providing a way to access data more quickly. It allows users to create indexes on specific fields in a collection, improving query performance by reducing the number of documents that need to be scanned.
8. What is the role of the Mongoose library in MongoDB?
Answer: Mongoose is an Object Data Modeling (ODM) library for MongoDB and Node.js. It provides a schema-based solution to model application data and interact with MongoDB, simplifying interactions and validations between the application and the database.
9. How does MongoDB ensure high availability and redundancy?
Answer: MongoDB ensures high availability and redundancy through features like Replica Sets. In a Replica Set, multiple nodes maintain the same data, allowing automatic failover and ensuring that the database remains available even if one node fails.
10. What are the primary components of the MongoDB architecture?
Answer: MongoDB architecture consists of:
- Database: Contains collections of documents.
- Collection: Group of MongoDB documents.
- Document: Basic unit of data in MongoDB, stored as BSON (Binary JSON) format.
- Replica Set: Group of MongoDB instances maintaining the same data set.
- Shard: Partition of data across multiple machines in a MongoDB cluster.