General

Question 1

What is MongoDB?

Answer 1

MongoDB is a NoSQL database program that uses JSON-like documents with optional schemas.

Question 2

What is a NoSQL database?

Answer 2

A NoSQL database provides a mechanism for storage and retrieval of data that is modeled in means other than the tabular relations used in relational databases.

Question 3

How does MongoDB store data?

Answer 3

MongoDB stores data in flexible, JSON-like documents, meaning fields can vary from document to document and data structure can be changed over time.

Question 4

What is a collection in MongoDB?

Answer 4

A collection is a group of MongoDB documents. It is the equivalent of an RDBMS table, but it doesn’t enforce any structure.

Question 5

What is a document in MongoDB?

Answer 5

A document is a record in a MongoDB collection, similar to a row in a table of an RDBMS.

Question 6

What is the purpose of BSON in MongoDB?

Answer 6

BSON (Binary JSON) is a binary-encoded serialization of JSON-like documents. It supports more data types than JSON.

Question 7

How does MongoDB handle indexing?

Answer 7

MongoDB supports various types of indexes including single field, compound, multikey, geospatial, text, hashed, clustered (>= v5.3) indexes.

Question 8

What is sharding in MongoDB?

Answer 8

Sharding is the process of storing data records across multiple machines to ensure horizontal scalability.

Question 9

What is replication in MongoDB?

Answer 9

Replication is the process of synchronizing data across multiple servers to provide redundancy and high availability.

Question 10

What is a replica set in MongoDB?

Answer 10

A replica set is a group of MongoDB instances that maintain the same data set, providing redundancy and high availability.

Question 11

What are the advantages of using MongoDB over relational databases?

Answer 11

Advantages include a flexible schema design, easier scalability, high performance for certain types of workloads, and simpler management of large datasets.

Question 12

What are the disadvantages of MongoDB?

Answer 12

Disadvantages include the potential for increased complexity in certain scenarios, less mature tooling compared to relational databases, and specific use cases where relational databases might be more efficient.

Question 13

What is the Aggregation Framework in MongoDB?

Answer 13

The Aggregation Framework is a set of operations that process data records and return computed results. It provides a way to transform and combine data.

Question 14

What is a primary key in MongoDB?

Answer 14

In MongoDB, the primary key is automatically set to the _id field in each document. Each document’s _id must be unique within a collection.

Question 15

How does MongoDB ensure ACID transactions?

Answer 15

MongoDB ensures ACID transactions at the document level and, starting with version 4.0, it supports multi-document transactions to provide atomicity, consistency, isolation, and durability across multiple documents.

Question 16

What are some common use cases for MongoDB?

Answer 16

Common use cases include content management, real-time analytics, Internet of Things (IoT) applications, mobile applications, and catalog management.

Question 17

What is the difference between MongoDB and MySQL?

Answer 17

MongoDB is a NoSQL, document-oriented database, while MySQL is a relational database management system (RDBMS). MongoDB uses JSON-like documents, whereas MySQL uses structured tables and rows.

Question 18

What is the role of the _id field in MongoDB?

Answer 18

The _id field in MongoDB serves as the primary key for a document in a collection. It uniquely identifies each document and is required in every document.

Question 19

How can you create a new database in MongoDB?

Answer 19

In MongoDB, a new database is created when you first store data in that database. You can switch to a new database using the use command, followed by the name of the database.

Question 20

What is a capped collection in MongoDB?

Answer 20

A capped collection is a fixed-size collection that maintains insertion order and, once the specified size limit is reached, overwrites the oldest documents.

Question 21

What is GridFS in MongoDB?

Answer 21

GridFS is a specification for storing and retrieving large files, such as images, videos, and documents, in MongoDB. It splits files into smaller chunks and stores each chunk as a separate document.

Question 22

How does MongoDB handle concurrency?

Answer 22

MongoDB uses a combination of multi-granularity locking, including reader-writer locks at the database, collection, and document levels, to manage concurrency.

Question 23

What is a MongoDB query language (MQL)?

Answer 23

MongoDB Query Language (MQL) is the language used to interact with MongoDB, allowing users to perform CRUD operations, query documents, and interact with the database.

Question 24

How do you update a document in MongoDB?

Answer 24

To update a document in MongoDB, you use the updateOne, updateMany, or replaceOne methods, specifying the criteria for the document(s) to update and the new values.

Question 25

What is a projection in MongoDB?

Answer 25

A projection in MongoDB is used to specify which fields to include or exclude in the returned documents when querying a collection.

Question 26

How can you delete documents in MongoDB?

Answer 26

You can delete documents in MongoDB using the deleteOne or deleteMany methods, specifying the criteria for the document(s) to delete.

Question 27

What is the purpose of the explain method in MongoDB?

Answer 27

The explain method provides detailed information about how MongoDB executes a query, including the query plan and performance statistics.

Question 28

What are some security features of MongoDB?

Answer 28

Security features of MongoDB include authentication, authorization, encryption, auditing, and IP whitelisting.

Question 29

What is the use of the $lookup operator in MongoDB?

Answer 29

The $lookup operator is used to perform left outer joins with other collections, allowing you to combine data from multiple collections in a single query.

Question 30

How do you back up a MongoDB database?

Answer 30

To back up a MongoDB database, you can use tools like mongodump to create binary dumps of the database, or perform file system snapshots, or use MongoDB Atlas’s built-in backup capabilities.

Question 31

What is a change stream in MongoDB?

Answer 31

A change stream allows applications to access real-time data changes in a collection, database, or deployment without polling the database.

Question 32

How can you ensure data consistency in MongoDB?

Answer 32

Data consistency in MongoDB is ensured through the use of replica sets, write concern settings, and transactions.

Question 33

What is the difference between find() and findOne() in MongoDB?

Answer 33

The find() method returns a cursor to all documents that match the query criteria, while the findOne() method returns only the first document that matches the query criteria.

Question 34

How does MongoDB handle schema changes?

Answer 34

MongoDB’s flexible schema allows for changes at the document level without affecting the entire database. Fields can be added or removed from documents as needed.

Question 35

What is the purpose of the $match stage in an aggregation pipeline?

Answer 35

The $match stage filters documents in an aggregation pipeline to pass only those documents that match the specified conditions to the next stage.

Question 36

How do you create an index in MongoDB?

Answer 36

To create an index in MongoDB, you use the createIndex method on a collection, specifying the fields to be indexed and the index type.