Top 60 MongoDB Interview Questions and Answers [2023]

If you are preparing for a job interview requiring skills in MongoDB, this article is going to be your one-stop-shop. Here you can learn about the definition of aggregation, sharding and splitting of the MongoDB, the procedure of creation of MongoDB schema, applications of MongoDB, the MongoDB structure in detail and many more. So let’s read the Top MongoDB Interview Questions and Answers.

Most Popular MongoDB Interview Questions and Answers:

  1. What points should be considered by one in the creation of a MongoDB schema?

In the process of MongoDB schema creation, One should take care of the following points:

  • Perform complex aggregate in the schema of MongoDB
  • Optimization of MongoDB schema for most frequent use cases
  • Not on read but on write do join
  • Keep the objects separate into different documents if it is not used together. If the objects are used together, then merge the objects into one document.
  • User requirement should be in mind while designing the MongoDB schema.
  1. What is the disadvantage in the MongoDB 32-bit versions?

The main disadvantage in the MongoDB 32-bit versions is the storage size. It is only limited to 2 GB storage sizes including the indexes and data when the 32-bit version of MongoDB is run. Therefore, production deployments are not possible on a 32-bit build of MongoDB.

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To deploy production, 64-bit builds strongly recommended as there is no limit to the size of storage virtually.

  1. Which language was used to develop MongoDB?

MongoDB was developed using C++. But many client libraries and drivers are using other languages. C Extensions are also used in some cases to improve the performance of drivers.

  1. What is the type of MongoDB Database?

MongoDB is a type of Database which is Document-oriented DBMS. It is similar to MySQL, which comprises the data model. MongoDB does not support transactions and Joins.

Fully-consistent reads, atomic writes on the per-document level, an expressive query language, secondary indexes are some of the features of MongoDB Database. Automated range-based partitioning is used for built-in horizontal scaling, and with automatic failover, master-slave replication is offered by MongoDB.

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  1. What are the benefits of MongoDB?
  • MongoDB is used in content management, real-time personalization, product catalogues, and mobile applications.
  • It is handy in deployments of multi-datacenter and requirements of extensive scalability.
  • MongoDB is beneficial for application where polymorphic data, semi-structured data, and unstructured data are used. In these cases, relational databases are not a good fit.
  • Ease of operation is excellent in MongoDB
  • It can scale which is not possible with relational databases.
  • For 60% to 80% of applications built today, MongoDB is a good fit for them
  • MongoDB can easily store primary data in real-time for operational uses.
  1. What is the disadvantage of MongoDB?

Some applications might not be a good fit for MongoDB, which requires scan-oriented and complex transaction applications using large data subsets. SQL and Relational data model applications cannot use MongoDB as a suitable replacement.

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  1. What is the difference between MySQL and MongoDB?

There are lots of differences in Normalization, speed performance, schema definition, and design, data querying, transaction, relationships and data representation of MySQL and MongoDB. MongoDB and MySQL are entirely different types of databases because one is a relational database, and the other is non-relational databases.

  1. What kind of DBMS is Mongo DB?

Document-Oriented DBMS is the kind of MongoDB.

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  1. What is the definition of the NoSQL Database?

NoSQL Database is the type of database that can sort and handle all kinds of complicated data, messy and unstructured data. The full form of NoSQL is “Not Only SQL”. It can solve the problem of significant users and big data in this age of heavy internet use. The traditional database management system cannot be used to bring a solution for Big Data processing at this age.

  1. Is MongoDB a NoSQL Database?

Yes, MongoDB is a NoSQL database.

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  1. What is the utilization of MongoDB?
  • Real-time analytics is possible in MongoDB
  • High-speed logging is the feature of MongoDB
  • With MongoDB, High scalability is possible
  • It can be easily used with relational database management system applications. Read more about MongoDB real world use cases.
  1. What is MongoDB?

MongoDB is a database that is document-oriented and used on cross-platform. It is classified as a NoSQL and is one of the most popular NoSQL database systems. It is better than the traditional table-based relational database structure. It favours JSON-like documents with dynamic schemas. A software company called 10gen developed MongoDB in 2007 as a service product.

Now this company has changed its name to MongoDB Inc. It is adopted as backed software for many services and websites after the developer company of MongoDB shifted it to an open-source development model. Some companies that chose MongoDB as backend software are the New York Times, Viacom, SourceForge, Foursquare, eBay, Craigslist and many more.

  1. Define the use of the save() method?

The method of replacing an existing document with a new document is called save() method.

  1. MongoDB data is stored in which format?

Collections are used to store data in MongoDB. It does not use tables to store data.

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  1. What is MongoDB Splitting?

The background process of keeping the chunks from becoming too large is called Splitting.

  1. What is MapReduce?

To process large quantities of data, a generic multi-phase data aggregation modality is used called MapReduce.

  1. What is Aggregation Pipeline?

The framework, which is to perform aggregation tasks for the transformation of documents into aggregated results, is called the aggregation pipeline.

  1. What is Auditing?

It is the capability of verifying the implementation of security policies to control the activities in the system.

  1. Explain the usage of dot notation in MongoDB?

Fields of an embedded document and elements of an array are accessed by using dot notation in MongoDB.

  1. How to restore the backup, and what is the command for it?

The backup can be restored by using a command called mongorestore.

  1. Describe the skip() method syntax ?

>db.COLLECTION_NAME.find().limit(NUMBER).skip(NUMBER) – This is syntax of skip() method.

  1. How to update a document into a collection?

There is a method to update a document into the collection, and those are save() method and update().

  1. Explain the usage of the DB command?

The use of the DB command gives the name of the selected database.

  1. Describe a MongoDB Collection?

A group of documents in MongoDB is called a collection.

  1. How is the backup of the database taken?

The backup of the database is taken by a command called mongodump command.

  1. Explain the syntax that is used for sorting documents?

>db.COLLECTION_NAME.find().sort({KEY:1}) is the sort() method syntax

  1. Explain the syntax that is used for limiting the records in database ?

>db.COLLECTION_NAME.find().limit(NUMBER) is the limit() method syntax

  1. Why limit() method is used?

Records in the database can be limited by using the limit() method.

  1. What is MongoDB Projection?

Necessary data in a document is selected by using MongoDB Projection without selecting the whole data of a report.

  1. How is a document removed from the collection?

There is a method to remove the document from a collection, and that method is called remove() method.

  1. Why is the pretty() method used?

The results are shown in a formatted way by using the pretty() method.

  1. What is the command to drop a database?

The command that is used to drop a database is called db.dropDatabse().

  1. How to create a database, and what is the command for it?

The database can be created by using a command, and that command is called Database_Name command.

  1. Explain about the Sharded cluster components?

There are three components in the sharded cluster, and they are Config Servers, Query routers, and Shards.

  1. What is Horizontal Scaling?

Data is distributed, and datasets are divided over many shards or servers by using Horizontal Scaling.

  1. Define Vertical Scaling?

Increasing capacity by the addition of more resources of storage and CPU is called Vertical Scaling.

  1. Define Replica set oplog?

The recording of the data modification operations in the replica set is called oplog records.

  1. How is an index created?

An Index is created by using a method called createIndex() method.

  1. Define Encryption of Storage?

Encrypting to ensure the protection of data through authorized processes on the operating system or the storage of MongoDB is called Storage encryption.

  1. What is an application-level Encryption?

Encryption within the application layer on a per-document basis and per-field basis is provided by application-level encryption.

  1. Define Embedded Documents?

Storage of related data to capture the relationship between data in the structure of a single document is called embedded documents.

  1. Explain the purpose of Replication?

The data availability is increased by redundancy, and it is achieved through Replication.

  1. Which type of data is stored by MongoDB?

The storage of data is done in the form of documents. The formats include value pairs and JSON-like field in the MongoDB. Difference between MongoDB and Hadoop

  1. Why is the Profiler used?

The characteristics of performance are shown against the database by using Profiler.

  1. What are secondary Replica sets?

The datasets of secondaries reflect the dataset of primary by applying the datasets’ operations and replicating the oplog of the primary replica set. This is called Secondary Replica Sets.

  1. What is Primary Replica Set?

The primary Replica accepts all the write operations from clients.

  1. How to see a connection?

db_adminCommand (“connPoolStats”) is the command that is used to see a connection.

  1. Why is Journaling in MongoDB used?

Safe Backups are taken by using the Journaling in MongoDB.

  1. Why is the GridFS in MongoDB used?

The retrieval and storage of large files such as video files, image file, audio file and many more are done by using GridFS.

  1. How to insert a document in MongoDB and what command to use?

There is a command to insert the document in MongoDB, and that command is database.collection.insert (document)

  1. Why is Index in MongoDB used for?

Indexes provide high-performance read operations in MongoDB for frequently used queries.

  1. What is Replication?

The process of synchronization of Data across different servers is called Replication.

  1. In MongoDB, What is the syntax to drop the collection?

In MongoDB, db.collection.drop() is the syntax used to drop the collection.

  1. How to create a collection in MongoDB?

A collection can be created by using a syntax and that syntax is dp.createCollection(name,options)

  1. In MongoDB, What is Namespace?

In MongoDB, Concatenation of the name of the database and collection name is called Namespace.

  1. In MongoDB, Define Aggregation?

Operations of processing the records of data and returning computed results are called aggregations in MongoDB.

  1. Define Sharding?

Storing of Data on different machines is called sharding in MongoDB.

  1. Define CRUD?

CRUD is an operation in MongoDB that provides

  • Create
  • Read
  • Update
  • Delete
  1. Define the key features of MongoDB?

The three features that are main in MongoDB are:

  • High availability
  • High performance
  • Automatic scaling
  1. Does an object attribute gets deleted from the database when it is removed?

Yes, An object attribute is deleted from the database when it is removed. One should always save the object again after the object attribute is eliminated.


So here are the most frequently asked MongoDB interview question. We ish you all the very best and hope this article will help you to crack your interview.

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What is MongoDB?

When we speak about database programs, MongoDB, an open-source relational database, counts as the most popular one. Nowadays, there is a significant rise in database storage, and to fulfill the data requirements, we have programs like MongoDB. One of the primary reasons for using MongoDB is that it has no SQL database program, which means you do not need to learn SQL to work with it. All the unstructured data inside MongoDB is stored in JSON format. Due to the program being open-source, it is accessible to everyone, making it a considerable choice to opt for. Furthermore, MongoDB has an interactive shell which makes accessing its datastore relatively easy.

Which one is better, MongoDB or SQL?

This is an important question that many of us constantly struggle with. Here’s a broader view of both to understand them better. SQL or NoSQL depends entirely on the kind of project you are working on and the data structures they are using. SQL stands for Structured Query Language and is generally considered best for structured RDMS to execute and manage structured data. When we shift to MongoDB, it is widely used by developers all over the world not only because it is popular but also due to its high scalability, high performance, and user-friendly database client. Therefore, depending on your requirements, you can choose whatever works best for you.

How secure is MongoDB?

Rest assured, MongoDB is a very secure database program where all the data is stored securely. In MongoDB, data is encrypted, and no one can decrypt it, not even MongoDB or other users. The entire database, along with its data, will only be available for users who have admin privileges of the database to manage, store and make changes in the available data. Moreover, to minimize risks, MongoDB owners don’t have the privilege to check or access their customers' sensitive information.

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