20 Basic questions on Mongodb.

 1. Question: What is MongoDB, and how does it differ from traditional relational databases?

   - Answer: MongoDB is a NoSQL document-oriented database. Unlike traditional relational databases, MongoDB stores data in flexible, JSON-like BSON documents and does not require a predefined schema.

 

2. Question: What is a BSON in MongoDB?

   - Answer: BSON (Binary JSON) is a binary-encoded serialization of JSON-like documents used in MongoDB. It supports additional data types, such as Date and Binary, compared to standard JSON.

 

3. Question: Explain the concept of a document in MongoDB.

   - Answer: In MongoDB, a document is a basic unit of data, similar to a row in a relational database. It is a JSON-like data structure that can contain various types of data, including nested documents and arrays.

 

4. Question: What is the purpose of an ObjectId in MongoDB?

   - Answer: ObjectId is a 12-byte identifier unique within a MongoDB instance. It is automatically generated and serves as the default primary key for documents, ensuring uniqueness.

 

5. Question: How does MongoDB ensure high availability and fault tolerance?

   - Answer: MongoDB achieves high availability through features like replica sets. A replica set consists of multiple nodes, and if one node fails, another can take over, ensuring continuous operation.

 

6. Question: What is the role of the `_id` field in MongoDB documents?

   - Answer: The `_id` field in MongoDB documents uniquely identifies each document in a collection. If not specified during document creation, MongoDB automatically assigns a unique ObjectId.

 

7. Question: Explain the difference between MongoDB sharding and replication.

   - Answer: Sharding involves distributing data across multiple machines to improve scalability, while replication involves creating copies of data on multiple servers to enhance fault tolerance and availability.

 

8. Question: How does indexing work in MongoDB, and why is it important?

   - Answer: MongoDB supports indexes to improve query performance. Indexes are created on fields, and they facilitate faster data retrieval by allowing MongoDB to locate and access data more efficiently.

 

9. Question: What is the aggregation framework in MongoDB?

   - Answer: The aggregation framework is a powerful tool in MongoDB for data transformation and analysis. It provides a set of operators to filter, group, project, and perform various transformations on data.

 

10. Question: What is the purpose of the `find()` method in MongoDB?

    - Answer: The `find()` method is used to query documents in a MongoDB collection. It allows specifying query criteria, projection, sorting, and other options to retrieve matching documents.

 

11. Question: Explain the concept of a MongoDB Atlas.

    - Answer: MongoDB Atlas is a fully managed cloud database service provided by MongoDB. It offers features like automated backups, monitoring, and scaling, making it easy to deploy and manage MongoDB in the cloud.

 

12. Question: How does MongoDB handle transactions, and what is a two-phase commit?

    - Answer: MongoDB supports multi-document transactions starting from version 4.0. A two-phase commit is a protocol used to ensure atomicity across multiple distributed nodes during a transaction.

 

13. Question: What is the role of the `mongod` process in MongoDB?

    - Answer: The `mongod` process is the MongoDB server daemon responsible for managing database operations. It handles requests from clients, performs data storage and retrieval, and manages data integrity.

 

14. Question: How does MongoDB handle schema evolution?

    - Answer: MongoDB's flexible schema allows for dynamic changes to documents without a predefined schema. Fields can be added or modified without affecting existing documents.

 

15. Question: What is a capped collection in MongoDB?

    - Answer: A capped collection in MongoDB is a fixed-size collection where older data is automatically replaced by newer data when the collection reaches its maximum size. It is often used for logs or other time-series data.

 

16. Question: Explain the role of the `db.collection.createIndex()` method in MongoDB.

    - Answer: The `db.collection.createIndex()` method is used to create indexes on specific fields in a collection. Indexes improve query performance by allowing MongoDB to quickly locate and access data.

 

17. Question: What is the purpose of the `mongorestore` command in MongoDB?

    - Answer: The `mongorestore` command is used to restore data previously created with `mongodump`. It imports BSON data into a MongoDB instance, recreating the data from a backup.

 

18. Question: How does MongoDB handle concurrency control and locking?

    - Answer: MongoDB uses a reader-writer lock to manage concurrency. Multiple readers can access data simultaneously, but write operations lock the database to ensure consistency.

 

19. Question: What is the role of the WiredTiger storage engine in MongoDB?

    - Answer: WiredTiger is the default storage engine in MongoDB from version 3.2 onward. It provides features like compression, document-level concurrency control, and efficient storage.

 

20. Question: How can you secure a MongoDB database?

    - Answer: MongoDB security measures include authentication, authorization, encryption of data in transit and at rest, role-based access control, and regular security audits. Additionally, firewalls and network security play crucial roles in securing MongoDB deployments.