MongoDB Interview Questions and Answers

MongoDB Interview Questions and Answers

Last updated on 27th Sep 2020, Blog, Interview Question

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If you’re looking for MongoDB Interview Questions for Experienced or Freshers, you are at right place. There are lot of opportunities from many reputed companies in the world. According to research MongoDB has a market share of about 4.5%. So, You still have the opportunity to move ahead in your career in MongoDB Development. ACTE offers Advanced MongoDB Interview Questions 2020 that helps you in cracking your interview & acquire dream career as MongoDB Developer.

1.Compare MongoDB and Cassandra

Ans:

MongoDB:

  • data mode are document
  • database scalability is read only
  • query of the data is multi-index

Cassandra:

  • data mode are big table like
  • database scalability is write only
  • query of the data is using key or scana

2.What makes mongodb best?

Ans:

It is considered a nosql database  because it is document oriented (do).

3.When do we use Namespace in MongoDB?

Ans:

database the namespace is used

4.when an index does not fit into RAM?

Ans:

Index is very huge then index will not fit to RAM.

5.If you remove an object attribute, is it deleted from the database?

Ans:

yes when the object attribute is delete then the object will be drop

6.What is the use of MongoDB?

Ans:

  •  MongoDB is typically used as the primary data store for operational applications with real-time requirements (i.e., low latency, high availability, etc.). MongoDB is generally a good fit for 60–80 percent of the applications we build today. MongoDB is easy to operate and scale in the ways that are hard if not impossible with relational databases.
  • MongoDB excels in many use cases where the relational databases aren’t a good fit, like applications with unstructured, semi-structured, and polymorphic data, as well as those with large scalability requirements or multi-datacenter deployments.
  • MongoDB may not be a good fit for some applications. For example, applications that require complex transactions (e.g., a double-entry bookkeeping system) and scan-oriented applications that access large subsets of the data mostly may not be a good fit for MongoDB. Also, MongoDB is not a drop-in replacement for legacy applications built around the relational data model and SQL.

7.What is the difference between MongoDB and MySQL?

Ans:

Although both MongoDB and MySQL are free and open-source databases, there is a lot of difference between them in terms of data representation, relationships, transaction, querying data, schema design and definition, performance speed, normalization, and many more. To compare MySQL with MongoDB is like a comparison between relational and non-relational databases.

8.What is meant by CRUD?

Ans:

create read update delete

9.What is sharding in MongoDB?

Ans:

The process of storing the record in multiple machines is known as sharing.

10.How can you see the connection used by Mongos?

Ans:

Mongos use db_adminCommand (“connPoolStats”.;

11.What are the limitations of the 32-bit versions of MongoDB?

Ans:

  • MongoDB uses memory-mapped files. When running a 32-bit build of MongoDB, the total storage size for the server, including data and indexes, is 2 GB. For this reason, we do not deploy MongoDB to production on 32-bit machines.
  • If we’re running a 64-bit build of MongoDB, there’s virtually no limit to the storage size. For production deployments, 64-bit builds and operating systems are strongly recommended.

12.How replication works in MongoDB?

Ans:

The process of synchronization across the multiple servers now has replication.

13.While creating Schema in MongoDB what are the points that need to be taken into consideration?

Ans:

Below are the following point need to be take care while creating the schema the combine objects into one document if you use them together for most frequent use cases optimize your schema

14.What is the syntax to create a collection?

Ans:

syntax:

  • db.create Collection(name,options)
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15.What is the syntax to drop a collection?

Ans:

syntax: To drop collection in MongoDB is

  • db.collection.drop()

16.Mention what is Object ld composed of?

Ans:

  • Timestamp
  • Client machine ID
  • Client process ID
  • byte increment counter

17.Mention what is the command syntax for inserting a document?

Ans:

syntax :

  • database.collection.insert (document..

18.What is the command syntax that tells you whether you are on the master server or not? And how many masters does MongoDB allow?

Ans:

  • Command syntax
  • isMaster()

19.Mention the command syntax that is used to view Mongo is using the link?

Ans:

syntax

  • db._adminCommand(“connPoolStats.”.

20.Mention what is the basic syntax to use index in MongoDB?

Ans:

  • db.COLLECTION_NAME.ensureIndex ( {KEY:1} ..

21.Explain what is GridFS in MongoDB?

Ans:

storing and retrieving large files such as images.

22.What are alternatives to MongoDB?

Ans:

  • Cassandr
  • CouchDB
  • Redis
  • Riak

23.What kind of NoSL database MongoDB is?

Ans:

It is a document oriented database.

24.Which all languages can be used with MongoDB?

Ans:

c,java,c++

25.How is MongoDB better than other SL databases?

Ans:

It Permits  highly flexible and scalable document structure. does not support such relationships.

26.Does MongoDB need a lot of RAM?

Ans:

It can run on small amounts of data because dynamic spaces are allocated and re-allocated.

27.What type of a DBMS is MongoDB?

Ans:

MongoDB is a document-oriented DBMS.

28.What do you understand about NoSQL databases? Is MongoDB a NoSQL database? Explain.

Ans:

Presently, the Internet is loaded with big data, big users, and so on that are becoming more complex day by day. NoSQL is the answer to all these problems; it is not a traditional database management system, not even a relational database management system (RDBMS).

  • NoSQL stands for ‘Not only SQL’, and it is a type of database that can handle and sort all types of unstructured, messy, and complicated data. It is just a new way to think about databases.
  • Yes, MongoDB is a NoSQL database.

29.How to create the database in MongoDB?

Ans:

Use Database name

Example: Use MYDB

30.How to show the entire database?

Ans:

Show dbs

31.What are the datatypes MongoDB supports?

Ans:

String, Integer, Boolean, Double, Array, Timestamp, Date, Regular expression

32.How to insert documents in Mongo DB collection?

Ans:

  • Db.dbname.insert(document)

33.How to display all the documents?

Ans:

  • Db.dbname.find(.

34.What is the purpose of the pretty () method?

Ans:

Pretty () method used to display in a formatted way.

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35.What is the use of limit ()?

Ans:

It will be used to limit the value displayed from the documents.

  • DB.DBNAME.find ().limit (number)

36.What are all the Aggregate functions in MongoDB?

Ans:

Sum, Avg, Min, Max, Push, addToSet, first, last

37.What is replication and why do we need it?

Ans:

It is the process of synchronizing data across multiple servers. It provides redundancy and increases data availability with multiple copies of data on different database server.WHY: To keep data safe, High availability of data, disaster recovery, No downtime for maintenance.

38.What is the syntax of sort() method?

Ans:

  • db.COLLECTION_NAME.find().sort({KEY:1}.

39.Which command is used to drop a database?

Ans:

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

40.What is the syntax to drop the collections?

Ans:

  • Db.collection.drop()

41.What are embedded documents?

Ans:

Embedded documents are received while they are small, given the relations between the related data has been written in one body.

42.Define application level encryption.

Ans:

Application Level Encryption provides encryption or per-per-written from the field in the application layer.

43.The encryption storage?

Ans:

MongoDB encryption encrypts data stored on any storage or processing by operating system may not be able to access protected data.

44.When everything is in no way sufficient data to get extended to multi-cut?

Ans:

That stands in a few MongoDB collections. Therefore, the list is kept in a lump of dough of all substances, it is either in size. It is only when there is an additional time slot, there will be no piece of information as a few choices, but the lump is more than 1, data is far from a lot of slices and can be extended up to 64 MB.

45.The judge in MongoDB and Couchbase and CouchbaseDB?

Ans:

When the common segment DB DB is Couchbase Couchbase Brunfelsia necessary in many ways, crossing points, all of which differ in the form of ecological duplications etc. As to the execution

46.Miâ on how we use MongoDB?

Ans:

By sequencing of the database, and the names of the pages linked from a specified collection is used.

47.If you remove an object attribute database wipes?

Ans:

So deleted. It is better to be safe to remove the attribute.

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

Ans:

Since, however, the present and the old files are converted to the backup file at the time of the acquisition moveChunk directory space.

49.Explain the situation with the index does not fit in RAM?

Ans:

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50.What MongoDB will provide consistency?

Ans:

The writer makes use of MongoDB is he that readeth, and the bolts of it, after allowing access one considers arbitrary or that any one that my readers may at the same time as the collection of a database. And it always brings access to private and hated by others.

51.Why did not MongoDB have a 32-bit system because he chose?

Ans:

a 32 bit candidate for a non-Brunfelsia DB is contained, that means running 32 bit with the MongoDB server, information and indexes require 2 GB. 32-bit, so it is not the only way to enter my thoughts.

52.How is working on Journaling MongoDB?

Ans:

There is nothing memory Journaling saved. The book on-disk files are really useful to have said that the route is habitual. DbPath interior is designed in the Journal subdirectory MongoDB.

53.How can we separate cursors’ connection with the written injustice?

Ans:

Snapshot () method is used to separate them from coming in with cursor writes. Here is a list of query and make sure everyone comes to be, and the manner of his mother tongue, there has been only to look at the article.

54.What is the use of the save() method?

Ans:

The save() method is used to replace the existing document with a new document.

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55.Explain the image set.

Ans:

I have to put the example of which is the group made up of Brunfelsia with the same knowledge of the set. To kill, and I need to provide high availability redundancy is the image of, and in the production of all of the deployments.

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

Ans:

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

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

Ans:

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

58.The sharding?

Ans:

Sharding to store data on multiple machines.

59.What is the sum of MongoDB?

Ans:

What matters are aggregations, process data records and return the results of counting.

60.To define the nominal distance mongodb?

Ans:

And what is the name of the collection database.

61.Syntax is used to create a collection mongodb?

Ans:

  • db.createCollection (name, options. is used to create a collection mongodb)

Syntax collection.

62.What is to drop the mongodb?

Ans:

  • db.collection.drop () is a collection to drop the mongodb.

63.Explain Infection.

Ans:

Infection by more synchronous processing of data servers.

64.What is the use of index mongodb?

Ans:

You can read a thing often used to provide a guideline for the high performance of queries.

65.The government should be inserted here because it is used?

Ans:

database.collection.insert (document) is used for inserting the document.

66.What is the use of GridFS mongodb?

Ans:

GridFS as I hear, is used for storage and for the most retrieving files, images, video files.

67.Journaling used?

Ans:

Journaling is the use of the back of the mongodb to be saved.

68.That the government used to bond?

Ans:

  • db_adminCommand ( “connPoolStats”.);

See the connection is not used.

69.Define the image killing?

Ans:

The first things were to write replicas but embraced the culture.

70.Define secondary image killing.

Ans:

Secondaries (page 565. Brands apply for the primary, and op oplog.

71.Select the MongoDB equivalent query for the below SL query – INSERT INTO employee (eid, age, salary. VALUES (763357, 45, 56489.40.;

Ans:

  • employee.insert( { eid: 763357, age: 45, salary: 56489.40 } .

72.Identify the invalid statement

Ans:

  • employee.insertMany( { [ emp_id:1, ename:”AAA” ] } .

73.An “inventory” collection has documents stored in MongoDB in the following format:

  • {_id:1,  status: “available”,items: [ { sku:”006548e8″, details: {……} }, { sku:”0067458e8″, details: {……}  }  ], stock level:35, seller: “aaa” }

 Which of the following commands can be used to find all the documents in the “inventory” collection having stock level from 20 to 50? [20 and 50 inclusive]

Ans:

  • inventory.find( { $nor: [ { stocklevel: { $lt:20 } },{ stocklevel:{ $gt:50 } } ] } ., db.
  • inventory.find ( { stocklevel : { $gte: 20, $lte: 50 } } .

74.Given the following documents in the electronics collection:

  • { _id: 1, item: “oven”, price: 14000,uantity: 5 }
  • { _id: 2, item: “LCD”, price: 48000, uantity: 10 }
  • { _id: 3, item: “refrigerator”, price: 25000, uantity: 4 }
  • { _id: 4, item: “LCD”, price: 56000, uantity: 3 }
  • { _id: 5, item: “LCD”, price: 20000, uantity: 9 }

Ans:

Updates only the first matching document

75.What would be the result of running the below query? – employee_profiles.deleteOne(   {‘unit’: ‘ETA’}.

Ans:

Only the first matching document is deleted

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76.The aggregation query in MongoDB that will sort the collection with the ename field ascending.

Ans:

  • employee.aggregate( [ { $sort: {ename:1} } ] .

77.The command that creates an index on the quantity field, descending

Ans:

  • inventory.createIndex( { “stock.quantity”:-1 } .

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

Ans:

MongoDB 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.

79.How does Journaling work in MongoDB?

Ans:

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.

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

Ans:

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.

81.What is Aggregation in MongoDB?

Ans:

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

82.Which syntax is used to create a Collection in MongoDB?

Ans:

We can create a collection in MongoDB using the following syntax:

  • db.createCollection(name,options)

83.Which syntax is used to drop a Collection in MongoDB?

Ans:

We can use the following syntax to drop a collection in MongoDB:

  • db.collection.drop()

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

Ans:

  • In MongoDB, indexes provide high-performance read operations for frequently used queries.
  • If you have any doubts or queries related to MongoDB, get them clarified from MongoDB Experts on our MongoDB Community!

85.Which command is used for inserting a document in MongoDB?

Ans:

The following command is used for inserting a document in MongoDB:

  • database.collection.insert (document)

86.What is the use of Journaling in MongoDB?

Ans:

Journaling is used for safe backups in MongoDB.

87.Which command is used to see a connection?

Ans:

We can use the following command to see the connection:

  • db_adminCommand (“connPoolStats”)

88.Define the primary Replica set.

Ans:

The primary replica set accepts all write operations from clients.

89.Define the secondary Replica sets.

Ans:

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.

90.What is the use of Profiler?

Ans:

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

91.What type of data is stored by MongoDB?

Ans:

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

92.What is the purpose of Replication?

Ans:

Replication provides redundancy, and it increases data availability.

93.Define the application-level Encryption.

Ans:

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

94.What is Storage Encryption?

Ans:

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

95.Which method is used to create an index?

Ans:

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

96.What is Replica set oplog?

Ans:

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

97.What is Vertical Scaling?

Ans:

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

98.Define Horizontal Scaling.

Ans:

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

99.What are the components of the Sharded cluster?

Ans:

The sharded cluster has the following components:

  • Shards
  • Query routers
  • Config servers

100.Which command is used to create a database?

Ans:

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

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