Top 100+ Mongodb Interview Questions And Answers

Question 1. What Are Nosql Databases? What Are The Different Types Of Nosql Databases?

Answer :

A NoSQL database affords a mechanism for garage and retrieval of facts that is modeled in method apart from the tabular family members utilized in relational databases (like SQL, Oracle, and many others.).

Types of NoSQL databases:

Document Oriented
Key Value
Graph
Column Oriented
Question 2. What Kind Of Nosql Database Mongodb Is?

Answer :

MongoDB is a record oriented database. It shops facts in the shape of BSON shape primarily based files. These files are saved in a set.

Python Interview Questions
Question three. Which Are The Most Important Features Of Mongodb?

Answer :

Flexible records version in shape of files
Agile and highly scalable database
Faster than conventional databases
Expressive question language
Question 4. What Is A Namespace In Mongodb?

Answer :

A Namespace is the concatenation of the database call and collection name. For e.G. College.Students with school as the database and students as the collection.

Python Tutorial
Question 5. Which All Languages Can Be Used With Mongodb?

Answer :

Currently, MonggoDB offers reputable motive force guide for C, C++, C#, Java, Node.Js, Perl, PHP, Python, Ruby, Scala, Go and Erlang. MongoDB can effortlessly be used with any of those languages. There are some other community supported drivers too however the above stated ones are formally provided by MongoDB.

C & Data Structures Interview Questions
Question 6. Compare Sql Databases And Mongodb At A High Level.?

Answer :

SQL databases shop statistics in shape of tables, rows, columns and facts. This records is stored in a pre-defined records version which is not very a great deal flexible for trendy real-world fantastically growing applications. MongoDB in contrast makes use of a flexible structure which may be without difficulty modified and extended.

Question 7. How Is Mongodb Better Than Other Sql Databases?

Answer :

MongoDB permits a enormously flexible and scalable document shape. For e.G. One information report in MongoDB may have 5 columns and the alternative one in the equal series will have ten columns. Also, MongoDB database are faster as compared to SQL databases due to efficient indexing and garage strategies.

Hadoop Tutorial Hadoop Interview Questions
Question 8. Compare Mongodb And Couchdb At High Level.?

Answer :

Although both of these databases are record orientated, MongoDB is a better desire for applications which need dynamic queries and properly performance on a totally large database. On the opposite facet, CouchDB is higher used for programs with on occasion converting queries and pre-described queries.

Question nine. Does Mongodb Support Foreign Key Constraints?

Answer :

No. MongoDB does not assist such relationships.

Node.Js Interview Questions
Question 10. Does Mongodb Support Acid Transaction Management And Locking Functionalities?

Answer :

No. MongoDB does not guide default multi-report ACID transactions. However, MongoDB presents atomic operation on a single report.

Node.Js Tutorial
Question 11. How Can You Achieve Primary Key - Foreign Key Relationships In Mongodb?

Answer :

By default MongoDB does now not aid such number one key - overseas key relationships. However, we will gain this idea via embedding one document internal some other. Foe e.G. An cope with file may be embedded inner consumer document.

Scala Interview Questions
Question 12. Does Mongodb Need A Lot Of Ram?

Answer :

No. MongoDB may be run even on a small quantity of RAM. MongoDB dynamically allocates and de-allocates RAM based totally at the requirements of different methods.

Python Interview Questions
Question thirteen. Does Mongodb Pushes The Writes To Disk Immediately Or Lazily?

Answer :

MongoDB pushes the facts to disk lazily. It updates the straight away written to the journal but writing the records from journal to disk happens lazily.

Scala Tutorial
Question 14. Explain The Structure Of Objectid In Mongodb.?

Answer :

ObjectID is a 12-byte BSON kind with:

four bytes price representing seconds
3 byte gadget identifier
2 byte technique id
3 byte counter
Question 15. Mongodb Uses Bson To Represent Document Structures. True Or False?

Answer :

True

Socket Programming Interview Questions
Question 16. If You Remove A Document From Database, Does Mongodb Remove It From Disk?

Answer :

Yes. Removing a record from database gets rid of it from disk too.

JSON (JavaScript Object Notation) Tutorial
Question 17. Mention The Command To Insert A Document In A Database Called School And Collection Called Persons.?

Answer :

use college;
db.People.Insert(  call: "kadhir", dept: "CSE"  )

NoSQL Interview Questions
Question 18. What Are Indexes In Mongodb?

Answer :

Indexes guide the efficient execution of queries in MongoDB. Without indexes, MongoDB ought to perform a group test, i.E. Experiment each file in a collection, to pick those documents that healthy the query declaration. If the perfect index exists for a query, MongoDB can use the index to restriction the number of documents it have to look into.

C & Data Structures Interview Questions
Question 19. How Many Indexes Does Mongodb Create By Default For A New Collection?

Answer :

By default, MongoDB created the _id series for each series.

HBase Tutorial
Question 20. Can You Create An Index On An Array Field In Mongodb? If Yes, What Happens In This Case?

Answer :

Yes. An array discipline can be listed in MongoDB. In this example, MongoDB could index every fee of the array.

JSON (JavaScript Object Notation) Interview Questions
Question 21. What Is A Covered Query In Mongodb?

Answer :

A blanketed query is the one in which:

fields used within the query are part of an index used within the question, and the fields again within the outcomes are in the identical index.

Question 22. Why Is A Covered Query Important?

Answer :

Since all of the fields are covered in the index itself, MongoDB can match the query circumstance in addition to return the result fields the usage of the equal index without searching inside the documents. Since indexes are saved in RAM or sequentially positioned on disk, such get entry to is a lot quicker.

Lucene Tutorial
Question 23. Does Mongodb Provide A Facility To Do Text Searches? How?

Answer :

Yes. MongoDB helps growing textual content indexes to support text search internal string content. This was a brand new function which could added in version 2.6.

HBase Interview Questions
Question 24. What Happens If An Index Does Not Fit Into Ram?

Answer :

If the indexes do now not fit into RAM, MongoDB reads information from disk that's pretty very tons slower than studying from RAM.

Hadoop Interview Questions
Question 25. Mention The Command To List All The Indexes On A Particular Collection.?

Answer :

db.Series.GetIndexes()

Question 26. At What Interval Does Mongodb Write Updates To The Disk?

Answer :

By default configuration, MongoDB writes updates to the disk each 60 seconds. However, this is configurable with the commitIntervalMs and syncPeriodSecs alternatives.

Solaris Administrator Interview Questions
Question 27. How Can You Achieve Transaction And Locking In Mongodb?

Answer :

To achieve concepts of transaction and locking in MongoDB, we can use the nesting of documents, additionally referred to as embedded files. MongoDB helps atomic operations within a unmarried report.

Node.Js Interview Questions
Question 28. What Is Aggregation In Mongodb?

Answer :

Aggregations operations system information records and return computed consequences. Aggregation operations organization values from a couple of documents together, and can carry out a spread of operations at the grouped records to go back a unmarried result. MongoDB provides three approaches to carry out aggregation: the aggregation pipeline, the map-reduce characteristic, and single reason aggregation methods and commands.

Question 29. What Is Sharding In Mongodb? Explain.?

Answer :

Sharding is a technique for storing data across a couple of machines. MongoDB makes use of sharding to aid deployments with very large information units and excessive throughput operations.

Question 30. What Is Replication In Mongodb?

Answer :

Replication is the technique of synchronizing statistics across more than one servers. Replication provides redundancy and will increase facts availability. With more than one copies of information on extraordinary database servers, replication protects a database from the loss of a single server. Replication also permits you to get over hardware failure and service interruptions.

Question 31. What Are Primary And Secondary Replica Sets?

Answer :

Primary and grasp nodes are the nodes that can receive writes. MongoDB's replication is 'single-grasp:' best one node can be given write operations at a time.

Secondary and slave nodes are read-only nodes that mirror from the number one.

Question 32. By Default, Mongodb Writes And Reads Data From Both Primary And Secondary Replica Sets. True Or False.

Answer :

False. MongoDB writes records best to the primary reproduction set.

Question 33. Why Are Mongodb Data Files Large In Size?

Answer :

MongoDB preallocate records documents to reserve area and avoid file device fragmentation whilst you setup the server.

Scala Interview Questions
Question 34. When Should We Embed One Document Within Another In Mongodb?

Answer :

You ought to do not forget embedding files for:

'contains' relationships between entities
One-to-many relationships
Performance reasons
Question 35. Why Mongodb Is Not Preferred Over A 32-bit System?

Answer :

When jogging a 32-bit construct of MongoDB, the full garage length for the server, including statistics and indexes, is two gigabytes. For this purpose, do not install MongoDB to manufacturing on 32-bit machines.
If you are jogging a sixty four-bit build of MongoDB, there may be truly no restrict to storage length.

Question 36. What Is A Storage Engine In Mongodb?

Answer :

A garage engine is the part of a database this is answerable for handling how statistics is stored on disk. For example, one garage engine would possibly provide better overall performance for read-heavy workloads, and every other might help a higher-throughput for write operations.

Socket Programming Interview Questions
Question 37. Which Are The Two Storage Engines Used By Mongodb?

Answer :

MongoDB uses MMAPv1 and WiredTiger.

Question 38. What Is The Role Of A Profiler In Mongodb? Where Does The Writes All The Data?

Answer :

The database profiler collects fine grained facts about MongoDB write operations, cursors, database commands on a walking mongod example. You can permit profiling on a according to-database or according to-example basis.

The database profiler writes all the facts it collects to the machine.Profile series, that is a capped series.

Question 39. How Does Journaling Work In Mongodb?

Answer :

When strolling with journaling, MongoDB shops and applies write operations in memory and inside the on-disk magazine earlier than the modifications are gift inside the facts files on disk. Writes to the journal are atomic, making sure the consistency of the on-disk journal documents. With journaling enabled, MongoDB creates a journal subdirectory inside the directory defined by dbPath, that is /records/db with the aid of default.

Question 40. Mention The Command To Check Whether You Are On The Master Server Or Not.?

Answer :

db.IsMaster()

NoSQL Interview Questions
Question forty one. Can You Configure The Cache Size For Mmapv1? How?

Answer :

No. MMAPv1 does no longer allow configuring the cache size.

Question forty two. How Does Mongodb Provide Concurrency?

Answer :

MongoDB uses reader-writer locks that allow concurrent readers shared get entry to to a useful resource, together with a database or collection, but provide one-of-a-kind get entry to to a unmarried write operation.

JSON (JavaScript Object Notation) Interview Questions
Question forty three. How Can You Isolate Your Cursors From Intervening With The Write Operations?

Answer :

You can use the snapshot() method on a cursor to isolate the operation for a completely particular case. Picture() traverses the index at the _id discipline and guarantees that the question will return every file no extra than as soon as.

Question 44. Can One Mongodb Operation Lock More Than One Databases? If Yes, How?

Answer :

Yes. Operations like copyDatabase(), repairDatabase(), and so on. Can lock greater than onne databases worried.

Question forty five. How Can Concurrency Affect Replica Sets Primary?

Answer :

In replication, while MongoDB writes to a group at the number one, MongoDB additionally writes to the primary's oplog, that's a special collection within the neighborhood database. Therefore, MongoDB need to lock both the collection's database and the local database.

Question 46. What Is Gridfs?

Answer :

GridFS is a specification for storing and retrieving files that exceed the BSON-record size limit of 16MB. Instead of storing a file in a unmarried file, GridFS divides a document into elements, or chunks, and stores every of these chunks as a separate file.

Question 47. Can You Run Multiple Javascript Operations In A Single Mongod Instance?

Answer :

Yes. The V8 JavaScript engine brought in 2.Four allows multiple JavaScript operations to run on the same time.

Question 48. Which Command Can Be Used To Provide Various Information On The Query Plans Used By A Mongodb Query?

Answer :

The explain() command may be used for this facts. The viable modes are: 'queryPlanner', 'executionStats', and 'allPlansExecution'.