MongoDB Interview Questions -

1. What makes MongoDB the best?

MongoDB is considered to be the best NoSQL database because of its following features:

1) Document-oriented (DO)
2) High performance (HP)
3) High availability (HA)
4) Easy scalability
5) Rich query language

2. How to do transactions/locking in MongoDB?

MongoDB does not use conventional locking with reduction as it is planned to be light, high-speed, and knowable in its presentation. It can be considered as parallel to the MySQL MyISAM auto entrust sculpt. With the simplest business sustain, performance is enhanced, particularly in a structure with numerous servers.

3. When and to what extent does data get extended to multi-slice?

MongoDB scrap stands on a collection. So, an album of all substances is kept in a lump or mass. Only when there is an additional time slot, there will be more than a few slice data achievement choices, but when there is more than one lump, data gets extended to a lot of slices and it can be extended to 64 MB.

4. Compare MongoDB with Couchbase and CouchbaseDB.

Although MongoDB, Couchbase, and Couchbase DB are common in many ways, still they are different in the case of necessities for the execution of the model, crossing points, storage, duplications, etc.

5. How does MongoDB provide consistency?

MongoDB uses the reader–writer locks, allowing simultaneous readers to access any supply like a database or a collection but always offering private access to single writes.

6. Explain the situation when an index does not fit into RAM.

When an index is too huge to fit into RAM, then MongoDB reads the index, which is faster than reading RAM because the indexes easily fit into RAM if the server has got RAM for indexes, along with the remaining set.

7. How can we move an old file into the moveChunk directory?

Once the functions are done, the old files are converted to backup files and moved to the moveChunk directory at the time of balancing the slices.

8. When do we use a namespace in MongoDB?

During the sequencing of the names of the database and the collection, the namespace is used.

9. Explain the replica set.

It is a group of mongo instances that maintains the same dataset. Replica sets provide redundancy and high availability and are the basis for all production deployments.

10. Define MongoDB.

It is a document-oriented database that is used for high availability, easy scalability, and high performance. It supports the dynamic schema design.

11. How can you isolate the cursors from intervening with the write operations?

The snapshot() method is used to isolate the cursors from intervening with writes. This method negotiates the index and makes sure that each query comes to any article only once.

12. How does Journaling work in MongoDB?

Write operations are saved in memory while journaling is going on. The on-disk journal files are really dependable for the reason that the journal writes are habitual. Inside dbPath, a journal subdirectory is designed by MongoDB.

13. Why is MongoDB not chosen for a 32-bit system?

Mongo DB is not considered as a 32-bit system because for running the 32-bit MongoDB, with the server, information and indexes require 2 GB. That is why it is not used in 32-bit devices.

14. Define Namespace in MongoDB.

It is the concatenation of the collection name and the name of the database.

15. What is Aggregation in MongoDB?

In MongoDB, aggregations are operations that process data records and return computed results.

16. What is Sharding?

In MongoDB, sharding means to store data on multiple machines.

17. What is CRUD?

MongoDB provides CRUD operations:

1) Create
2) Read
3) Update
4) Delete

18. What are the key features of MongoDB?

There are three main features of MongoDB:

1) Automatic scaling
2) High performance
3) High availability

Intermediate Interview Questions

19. Define the secondary Replica sets.

The secondaries replicate the primary replica set’s oplog and apply the operations to their datasets such that the secondaries’ datasets reflect the primary’s dataset.

20. Define the primary Replica set.

The primary replica set accepts all write operations from clients.

21. What is the use of Journaling in MongoDB?

Journaling is used for safe backups in MongoDB.

22. What is the use of GridFS in MongoDB?

GridFS is used for storing and retrieving large files, such as audio, image, and video files.

23. What is the use of an Index in MongoDB?

In MongoDB, indexes provide high-performance read operations for frequently used queries.

24. Explain Replication.

Replication is the process of synchronizing data across multiple servers.

25. What is the use of Profiler?

Profiler is used to show the performance characteristics of every operation against the database.

26. What type of data is stored by MongoDB?

MongoDB stores data in the form of documents, which are JSON-like field and value pairs.

27. What is the purpose of Replication?

Replication provides redundancy, and it increases data availability.

28. What are Embedded documents?

Embedded documents capture relationships between data by storing related data in a single document structure.

29. Define the application-level Encryption.

The application-level encryption provides encryption on a per-field or per-document basis within the application layer.

30. What is Storage Encryption?

Storage encryption encrypts all MongoDB data on storage or on the operating system to ensure that only authorized processes can access the protected data.

31. Define Horizontal Scaling.

Horizontal scaling divides the dataset and distributes data over multiple servers, or shards.

32. What is Vertical Scaling?

Vertical scaling adds more CPU and storage resources to increase capacity.

33. What is Replica set oplog?

The oplog records all operations that modify the data in the replica set.

34. Which method is used to create an index?

The createIndex() method is used to create an index.

Advanced Interview Questions

35. Which method is used to remove a document from a collection?

The remove() method is used to remove a document from a collection.

36. What is the use of the pretty() method?

The pretty() method is used to show the results in a formatted way.

37. Which command is used to drop a database?

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

38. Which command is used to create a database?

To create a database, we can use the Database_Name command.

39. What are the components of the Sharded cluster?

The sharded cluster has the following components:

1) Shards
2) Query routers
3) Config servers

40. Define MongoDB Projection.

Projection is used to select only the necessary data. It does not select the whole data of a document.

41. What is the use of the limit() method?

The limit() method is used to limit the records in the database.

42. Which command is used to create a backup of the database?

The mongodump command is used to create a backup of the database.

43. Which method is used to update documents into a collection?

The update() and save() methods are used to update documents into a collection.

44. What is the use of the db command?

The db command gives the name of the currently selected database.

45. What is a Collection in MongoDB?

In MongoDB, a collection is a group of MongoDB documents.

46. Which command is used to restore the backup?

The mongorestore command is used to restore the backup.

47. What is the use of the dot notation in MongoDB?

MongoDB uses the dot notation to access the elements of an array and the fields of an embedded document.

48. Define Auditing.

Auditing provides administrators with the ability to verify that the implemented security policies are controlling the activity in the system.

49. Define MapReduce.

MapReduce is a generic multi-phase data aggregation modality that is used for processing quantities of data.

50. What is Splitting in MongoDB?

Splitting is a background process that is used to keep chunks from growing too large.

Top 50 MongoDB Interview Questions and Answers