MongoDB Interview Questions & Answers

A warm welcome to the MongoDB Interview Questions & Answers course by Uplatz.

Uplatz brings you this training on the most commonly asked interview questions and answers on MongoDB.

By learning and understanding deeply the popular interview questions (with answers) of MongoDB, you can confidently apply for Web Developer / Mongo Programmer / Full Stack Engineer (MERN, MEAN stacks) / Database Developer roles.

This course explains the solutions to common questions asked in the recent MongoDB Programmer and Web Developer interviews and comes with a freely downloadable booklet on the same.

MongoDB interview questions tutorial will help you crack the job interviews which can be a turning point in your career!

With these top hand-picked MongoDB interview questions, you will be able to gain sound knowledge on MongoDB concepts and their application. As part of these interview questions, you will understand the detailed structure of MongoDB, what its different applications are, how to create a schema in MongoDB, what splitting is, sharding and aggregation in Mongo database, and many more.

Background

MongoDB is a document-oriented NoSQL database used for high volume data storage. MongoDB is a database which came into light around the mid-2000s. It falls under the category of a NoSQL database. In other words, MongoDB is an open-source document-based database management tool that stores data in JSON-like formats. It is a highly scalable, flexible, and distributed NoSQL database.

With the rise in data all around the world, there has been an observable and increasing interest surrounding the wave of the non-relational database, also known as ‘NoSQL‘. Businesses and organisations are seeking new methods to manage the flood of data and are drawn toward the alternate database management tools and systems that are different from the traditional relational database systems. Here comes MongoDB into the picture.

Some of the key features of MongoDB are:

1. Each database contains collections which in turn contains documents. Each document can be different with a varying number of fields. The size and content of each document can be different from each other.
2. The document structure is more in line with how developers construct their classes and objects in their respective programming languages. Developers will often say that their classes are not rows and columns but have a clear structure with key-value pairs.
3. As seen in the introduction with NoSQL databases, the rows (or documents as called in MongoDB) doesn’t need to have a schema defined beforehand. Instead, the fields can be created on the fly.
4. The data model available within MongoDB allows you to represent hierarchical relationships, to store arrays, and other more complex structures more easily.
5. Scalability – The MongoDB environments are very scalable. Companies across the world have defined clusters with some of them running 100+ nodes with around millions of documents within the database
6. Queries: It supports ad-hoc queries and document-based queries.
7. Index Support: Any field in the document can be indexed.
8. Replication: It supports Master–Slave replication. MongoDB uses native application to maintain multiple copies of data. Preventing database downtime is one of the replica set’s features as it has self-healing shard.
9. Multiple Servers: The database can run over multiple servers. Data is duplicated to foolproof the system in the case of hardware failure.
10. Auto-sharding: This process distributes data across multiple physical partitions called shards. Due to sharding, MongoDB has an automatic load balancing feature.
11. MapReduce: It supports MapReduce and flexible aggregation tools.
12. Failure Handling: In MongoDB, it’s easy to cope with cases of failures. Huge numbers of replicas give out increased protection and data availability against database downtime like rack failures, multiple machine failures, and data center failures, or even network partitions.
13. GridFS: Without complicating your stack, any sizes of files can be stored. GridFS feature divides files into smaller parts and stores them as separate documents.
14. Schema-less Database: It is a schema-less database written in C++.
15. Document-oriented Storage: It uses BSON format which is a JSON-like format.
16. Procedures: MongoDB JavaScript works well as the database uses the language instead of procedures.

MongoDB Interview Questions (some examples)

Some of the popular MongoDB interview questions asked in Full Stack Developer job interviews are:

1. What is MongoDB?

MongoDB is a document-based database which is highly scalable and offers better performance.

2. Define a replica set

The group of instances which host similar data set is known as a replica set. Two nodes are present in a replica set, one is secondary and the other is primary, where data is replicated from primary and sent to the secondary node.

3. What is the role of profiler in MongoDB?

The role of a MongoDB profiler is to show the performance and analyse the characteristics of every operation of the database. By using the profiler, you will find all the queries which are slower than usual.

4. What are NoSQL databases? What are the different types of NoSQL databases?

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 (like SQL, Oracle, etc.).

5. What are the different types of NoSQL databases? Give some examples.

The NoSQL database is classified into four basic types:

• Column store
• Document store
• Key-value store
• Graph base

The following are the few examples of NoSQL database:

• MongoDB
• Cassandra
• CouchDB
• HBASE

6. What kind of NoSQL database MongoDB is?

MongoDB is a document oriented database. It stores data in the form of BSON structure based documents. These documents are stored in a collection.

7. What are the key features of MongoDB?

The following are the core features of MongoDB:

• High performance
• Automatic scaling
• Rich query language
• High availability

8. What is the advantage of MongoDB?

The following are a few advantages of MongoDB database:

• Schema less
• Easy to scale-out
• No complex joins
• Structure of a single object is clear

9. How is MongoDB better than other SQL databases?

MongoDB allows a highly flexible and scalable document structure. For e.g. one data document in MongoDB can have five columns and the other one in the same collection can have ten columns. Also, MongoDB database are faster as compared to SQL databases due to efficient indexing and storage techniques.

10. Which programming languages can be used with MongoDB?

MongoDB works with all the programming languages such as C, C++, C#, Java, Node.js, Perl, PHP, Python, Ruby, Scala, Go, Erlang.

11. What is the difference between MongoDB and CouchDB?

Although both databases are document oriented, MongoDB is a better choice for applications that need dynamic queries and good performance on a very big database. On the other side, CouchDB is better used for applications with occasionally changing queries and pre-defined queries.

12. What is an embedded document?

Embedded documents specify the relationship between data that is written inside the body. The documents are received while the related data body is small.