MongoDB Interview Questions and Answers

MongoDB Interview Questions and Answers, What is Mongodb?, Features of Mongodb, SQL vs. NoSQL databases, document databases, and use Mongdb.

When dealing with data, there are two types of data as we know – (i) structured data and (ii) unstructured data. Structured data is usually stored in a tabular form whereas unstructured data is not. To manage huge sets of unstructured data like log or IoT data, a NoSQL database is used.

MongoDB Interview Questions and Answers

1. What Is MongoDB?

MongoDB is developed by MongoDB Inc. and licensed under the Server Side Public License (SSPL).

It is an open-source NoSQL database, document database written in C++ language. It uses JSON-like documents with optional schemas.

We have four main types of NoSQL databases:

Document databases
Key-value stores
Column-oriented databases
Graph databases

2. Where is MongoDB used?

MongoDB is widely used for storing product information and details by finance and e-commerce companies. You can even store the product catalogue of your brand in it.

MongoDB can also be used to store and model machine-generated data (Ex: Log data and IOT data).

MongoDB is ideal for cloud computing. Cloud-based storage needs to easily distribute data across multiple servers, which suits MongoDB’s nature perfectly.

3. What are Databases in MongoDB?

MongoDB groups collections into databases. MongoDB can host several databases, each grouping together collections.

Some reserved database names are as follows:


4. What is the Mongo Shell?

Mongo shell is the JavaScript shell that helps to configure, query, connect and work with the MongoDB database from the command line. It is an open-source standalone utility under Apache 2 license.

5. Which are the most important features of MongoDB?

Flexible data model in form of documents
Agile and highly scalable database
Faster than traditional databases
Expressive query language

6. Why MongoDB is the best NoSQL database?

MongoDB is the best NoSQL database due to the following features:

High Performance
High Availability
Easily Scalable
Rich Query Language
Document Oriented

7. Which all languages can be used with MongoDB?

Currently, MonggoDB provides official driver support for C, C++, C#, Java, Node.js, Perl, PHP, Python, Ruby, Scala, Go and Erlang.

8. How data is added in MongoDB?

insertOne() method is used to insert document (data record) into a collection. In case collection does not exist, insertOne() method creates collection.

Syntax for adding data record in collection is:

database.collection.insert (document).

9. Explain what are indexes in MongoDB?

Indexes are special structures in MongoDB, which stores a small portion of the data set in an easy to traverse form. Ordered by the value of the field specified in the index, the index stores the value of a specific field or set of fields.

10. How can you achieve Primary Key – Foreign Key relationships in MongoDB?

By default MongoDB does not support such primary key – foreign key relationships. However, we can achieve this concept by embedding one document inside another (aka subdocuments).

11. What specifically is a collection in MongoDB?

A group of documents is referred to as a collection. If a document is the MongoDB analog of a row in a relational database, then a collection is the MongoDB analog of a table.

12. What is the role of profiler in MongoDB?

MongoDB includes a database profiler which shows performance characteristics of each operation against the database. With this profiler you can find queries (and write operations) which are slower than they should be and use this information for determining when an index is needed.

13. explain various data types in MongoDB?

The data types used in MongoDB are listed below:

String: UTF-8 compliant strings values can be stored in the MongoDB database.

Integer: Saves numerical values of 32 or 64 bit based on the server.

Double: Floating point values.

Boolean: Stores Boolean values such as True/False.

Null: Null value can be stored.

Array: Multiple values in one key can be stored.

Object: Embedded documents are stored as Object.

Object ID: Document ID can be stored in object Id data type.

Binary Data: Data stored in 0s and 1s format, e.g. byte (unit for storing electronic memory).

14. List CRUD operations by MongoDB?

CRUD is the abbreviation as explained C- Create, R – Read, U – Update, and D – Delete.

The commands for each of these operations are as below:

C – Create – db.collection_name.insert();

R – Read – db.collection_name.find();

U – Update – db.collection_name.update();

D – Delete – db.collection_name.remove({“field-name” : “value” });

15. How do MongoDB store images, videos, and other large files?

Images, Videos, and other large-size files are stored in GridFS specification. GridFS divides large files into chunks or parts. These chunks are stored as a separate documents.

16. What is MapReduce in MongoDB?

MapReduce is an algorithm used for deducing some useful information and trends from the available data. It is generally used in data analytics associated with Big Data.

17. Can you run multiple Mongo Instances on the same computer?

Yes. Using different port number for each Mongo Instance, multiple instances can be started.

18. How do you create a MongoDB Database?

MongoDB Database can be created through Mongo Shell using use <database_name> command. If the database_name provided to the use command does not exist, a new database is created.

Technically, a database is not created until a document is inserted to a collection in the database.

19. How to Create Queries in MongoDB?

Using find() method, pretty() method, and findOne() method you can query the data from the MongoDB collection.

20. What Are Embedded Documents in MongoDB?

Embedded documents in MongoDB allow you to store all kinds of information related to each other in a single document. An embedded (nested) MongoDB Document is a normal document that resides inside another document within a MongoDB collection.

MongoDB Interview Questions and Answers


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