MongoDB is a NoSQL database and is very popular in the IT industry. So, we decided to give you a definitive list of MongoDB interview questions and answers which are most likely to be asked in your next interview.
1. What is MongoDB?
MongoDB is a NoSQL cross-platform document-based database program. It’s highly scalable, easily available and has a higher performance than any other database.
2. What is a replica set?
As the name suggests, a replica set is a group of mongo that hosts the same data set. A replica set contains a primary node and a secondary node. Both nodes have replicated data.
3. Explain replication in MongoDB.
Replication is known as the process of synchronization of data across multiple servers.
It helps in safeguarding the database from the loss of a single server.
Replication offers redundancy and increases the availability of data with several copies of data on a different database server.
4. When would you use a namespace in MongoDB?
A namespace is used during the sequencing of names of database and collection.
5. How does MongoDB provide consistency?
MongoDB relies on reader-writer locks which ensures that simultaneous readers have access to any supplies like a database or a collection but still provides private access to single writes.
6. Mention the points that should be taken into consideration when creating Schema in MongoDB.
The points that need to be kept in mind while creating Schema are:
- The design should be according to user requirements.
- Complex aggregation in Schema is a must.
- Deploy joins while write and not when it is read.
- Optimize Schema as per the use cases.
- Combine objects when using them together or else, separate them.
7. Mention the syntax to create a collection and to drop a collection in MongoDB.
Syntax questions are pretty common in MongoDB interview questions.
The syntax to create a collection and to drop a collection are:
db.createCollection(name,options)
db.collection.drop()
8. What is the syntax for inserting a document?
The syntax for inserting a document is:
database.collection.insert(document)
9. Explain the role of profiler in MongoDB.
The profiler in MongoDB reveals the performance characteristics of every operation against the database. You can also determine slower queries than the usual.
10. Which feature in MongoDB is used to do a safe backup?
Journaling is the feature used to do safe backups in MongoDB.
11. How to inspect the source code of a function?
The only way to inspect the source code of a function without parentheses is when the function is invoked.
12. What is the use of Journaling in MongoDB?
The sole purpose of Journaling is to keep safe backups in MongoDB.
13. Explain how Journaling works in MongoDB.
Journaling is ongoing while write operations are being saved in the memory.
The Journal writes are habitual which is why the on-disk journal is dependent.
A journal subdirectory is created inside the dbPath by MongoDB.
14. Name the key features of MongoDB.
The key features of MongoDB are:
- High availability
- Automatic scaling
- High performance
15. What does CRUD mean in the context of MongoDB?
CRUD in MongoDB means:
- Create
- Read
- Update
- Delete
16. Which syntax is used to drop a collection MongoDB?
The syntax used to drop a collection MongoDB is:
db.collection.drop()
17. What is the use of an index in MongoDB?
This question is probably the most commonly asked as MongoDB interview questions.
Indexes improve efficiency in terms of searching within a database.
An index is created based on certain fields of a document.
It’s a special data structure, so when search operations are performed, instead of searching an entire document it searches indexes.
18. What is MongoDB Atlas?
MongoDB Atlas is a fully-managed cloud operational database developed by the same team as MongoDB.
Atlas handles the intricacies of deploying, healing and managing deployments on any cloud service provider such as AWS, Azure, GCP etc.
19. What is MongoDB Compass?
MongoDB Compass is the Graphical User Interface (GUI) for MongoDB, which helps users to analyze and manage their data without any prior knowledge of MongoDB query syntax.
20. Mention the command used to see a connection.
The command to see a connection is:
db._adminCommand(“connPoolStats.”)
21. What are embedded documents?
Embedded documents store relational data in a single document structure to showcase the captured relationship between data.
22. What is application-level encryption?
Application-level encryption is used within an application layer to encrypt a particular field or document.
23. Define Vertical Scaling.
Vertical Scaling increases the capacity by adding more CPU and storage resources.
24. What is storage encryption?
Storage encryption is done to protect the data from being accessed by any unauthorized processes.
Storage encryption encrypts all data on MongoDB storage so that only authorized process can access it.
25. What is MongoDB Projection?
Projection only selects the necessary data and excludes the rest of the data in a document.
26. What is the syntax of the limit() method?
The syntax of the limit() method is:
db.COLLECTION_NAME.find().limit(number)
27. What is a Collection in MongoDB?
A group of MongoDB documents is called a Collection.
28. Mention the use of db command in MongoDB.
The db command signifies the currently selected database.
29. What is the syntax of the skip() method?
The syntax of the skip() method is:
db.COLLECTION_NAME.find().limit(number).skip(number)
30. Which language is MongoDB based on?
C++ is the language used to write and implement MongoDB.
31. Define MapReduce.
It is a data processing paradigm used for condensing large volumes of data into aggregated results.
