Jump To Right Section Show

On this article, we’ll give consideration to a lot of necessary MongoDB Interview Questions that you would be be requested all through a NoSQL database job interview. Let’s see 45 very commonly requested mongo interview questions & solutions as underneath:

1) What do you perceive by NoSQL databases? Is MongoDB a NoSQL database? clarify.

Nowadays, the web is loaded with large information, large customers, large complexity, and so on., and in addition turning into extra complicated daily. NoSQL is the reply to all these issues, It isn’t a standard database management system, not even a relational database administration system (RDBMS). NoSQL stands for “Not Solely SQL”. NoSQL is a kind of database that may deal with and type all kinds of unstructured, messy, and complex information. It’s only a new manner to consider the database. Sure. MongoDB is a NoSQL database.

2) That are the totally different languages supported by MongoDB?

MongoDB supplies official driver help for C, C++, C#, Java, Node.js, Perl, PHP, Python, Ruby, Scala, Go, and Erlang. You need to use MongoDB with any of the above languages. There are another community-supported drivers too however the above-mentioned ones are formally supplied by MongoDB.

3) What are the various kinds of NoSQL databases? Give some examples.

NoSQL database will be categorized into 4 primary sorts:

  1. Key-value retailer NoSQL database
  2. Doc retailer NoSQL database
  3. Column retailer NoSQL database
  4. Graph based mostly NoSQL database

There are various NoSQL databases. MongoDB, Cassandra, CouchDB, Hypertable, Redis, Riak, Neo4j, HBase, Couchbase, MemcacheDB, Voldemort, RevenDB, and so on. are the examples of NoSQL databases.

4) Is MongoDB higher than different SQL databases? If sure then how?

MongoDB is healthier than different SQL databases as a result of it permits a extremely versatile and scalable doc construction.

For instance:

  • One information doc in MongoDB can have 5 columns and the opposite one in the identical assortment can have ten columns.
  • MongoDB databases are faster than SQL databases because of environment friendly indexing and storage strategies.
5) What sort of DBMS is MongoDB?

MongoDB is a document-oriented DBMS

6) What’s the distinction between MongoDB and MySQL?

Though MongoDB and MySQL each are free and open-source databases, there’s a whole lot of distinction between them within the time period of knowledge illustration, relationship, transaction, querying information, schema design and definition, efficiency pace, normalization and lots of extra. To match MySQL with MongoDB is sort of a comparability between Relational and Non-relational databases.

7) Why MongoDB is called the very best NoSQL database?

MongoDB is the very best NoSQL database as a result of it’s:

  • Doc Oriented
  • Wealthy Question language
  • Excessive Efficiency
  • Extremely Out there
  • Simply Scalable
8) Does MongoDB help primary-key, foreign-key relationships?

No. By Default, MongoDB does not help the primary key-foreign key relationships.

9) Are you able to obtain main key – overseas key relationships in MongoDB?

We will obtain a primary key foreign key relationship by embedding one doc inside one other. For instance, An tackle doc will be embedded inside a buyer doc.

10) Does MongoDB want a whole lot of RAM?

No. There isn’t a want for lots of RAM to run MongoDB. It may be run even on a small quantity of RAM as a result of it dynamically allocates and de-allocates RAM in keeping with the requirement of the processes.

11) Clarify the construction of ObjectID in MongoDB.

ObjectID is a 12-byte BSON sort. These are:

  • 4 bytes worth representing seconds
  • 3 byte machine identifier
  • 2 byte course of id
  • 3 byte counter
12) Is it true that MongoDB makes use of BSON to symbolize doc construction?


13) What are Indexes in MongoDB?

In MongoDB, Indexes are used to execute queries effectively. With out indexes, MongoDB should carry out a set scan, i.e. scan each doc in a set, to select those documents that match the query statement. If an acceptable index exists for a question, MongoDB can use the index to restrict the variety of paperwork it should examine.

14) By default, which index is created by MongoDB for each assortment?

By default, the_id assortment is created for each assortment by MongoDB.

15) What’s a Namespace in MongoDB?

A namespace is a concatenation of the database identify and the gathering identify. Assortment, through which MongoDB shops BSON objects.

16) Can journaling options be used to carry out secure scorching backups?


17) Why does Profiler use in MongoDB?

MongoDB makes use of a database profiler to carry out the traits of every operation in opposition to the database. You need to use a profiler to seek out queries and write operations

18) When you take away an object attribute, is it deleted from the database?

Sure, it’s. Take away the attribute after which re-save() the thing.

19) Through which language MongoDB is written?

MongoDB is written and applied in C++.

20) Does MongoDB want a whole lot of house of Random Entry Reminiscence (RAM)?

No. MongoDB will be run on a small free house of RAM.

21) What language you need to use with MongoDB?

MongoDB consumer drivers help all the favored programming languages so there is no such thing as a difficulty of language, you need to use any language that you really want.

22) Does the MongoDB database have tables for storing information?

No. As a substitute of tables, MongoDB makes use of “Collections” to retailer information.

23) Do the MongoDB databases have a schema?

Sure. MongoDB databases have dynamic schema. There isn’t a have to outline the construction to create collections.

24) What’s the technique to configure the cache dimension in MongoDB?

MongoDB’s cache will not be configurable. Really, MongoDB makes use of all of the free areas on the system automatically by way of memory-mapped files.

25) Learn how to do Transaction/locking in MongoDB?

MongoDB does not use conventional locking or complicated transaction with Rollback. MongoDB is designed to be gentle weighted, quick, and predictable to its efficiency. It retains transaction help merely to reinforce efficiency.

26) Why 32-bit model of MongoDB will not be most well-liked?

As a result of MongoDB makes use of memory-mapped recordsdata so whenever you run a 32-bit construct of MongoDB, the overall storage dimension of the server is 2 GB. However whenever you run a 64-bit construct of MongoDB, this supplies just about limitless storage dimension. So 64-bit is most well-liked over 32-bit.

27) Is it doable to take away previous recordsdata within the moveChunk listing?

Sure, These recordsdata will be deleted as soon as the operations are performed as a result of these recordsdata are made as backups throughout regular shard balancing operations. This can be a handbook cleanup course of and essential to unencumber house.

28) What must do if a shard is down or gradual and also you do a question?

If a shard is down and also you even do question then your question shall be returned with an error until you set a partial question possibility. But when a shard is gradual them Mongos will watch for them until response.

29)Clarify the lined question in MongoDB.

A question is named a lined question if satisfies the next two circumstances:

  • The fields used within the question are a part of an index used within the question.
  • The fields returned within the outcomes are in the identical index.
30) What’s the significance of the lined question?

A lined question makes the execution of the question quicker as a result of indexes are saved in RAM or sequentially positioned on a disk. It makes the execution of the question quicker. Lined question makes the fields are lined within the index itself, MongoDB can match the question situation in addition to return the end result fields utilizing the identical index with out trying contained in the paperwork.

31) What’s sharding in MongoDB?

In MongoDB, Sharding is a procedure of storing information information throughout a number of machines. It’s a MongoDB method to fulfill the calls for of knowledge progress. It creates a horizontal partition of data in a database or search engine. Every partition is known as a shard or database shard.

32) What’s a reproduction set in MongoDB?

A duplicate will be specified as a gaggle of mongo situations that host the identical information set. In a reproduction set, one node is main, and one other is secondary. All information is replicated from main to secondary nodes.

33) What are main and secondary replicas set in MongoDB?

In MongoDB, main nodes are the node that may settle for write. These are also referred to as grasp nodes. The replication in MongoDB is a single grasp so, just one node can settle for write operations at a time. Secondary nodes are referred to as slave nodes. These are read-only nodes that replicate from the first.

34) By default, which duplicate units are used to write down information?

By default, MongoDB writes information solely to the first duplicate set.

35) What’s CRUD in MongoDB?

MongoDB helps the next CRUD operations:

  • Create
  • Learn
  • Replace
  • Delete
36) Through which format MongoDB represents doc construction?

MongoDB makes use of BSON to symbolize doc buildings.

37) What is going to occur whenever you take away a doc from the database in MongoDB? Does MongoDB take away it from the disk?

Sure. When you take away a doc from the database, MongoDB will take away it from the disk too.

38) Why are MongoDB information recordsdata giant in dimension?

MongoDB does not comply with file system fragmentation and pre-allocates information recordsdata to order house whereas establishing the server. That is why MongoDB information files are large in size.

39) What’s a storage engine in MongoDB?

A storage engine is the a part of a database that’s used to handle how information is saved on a disk.

For instance, one storage engine would possibly supply higher efficiency for read-heavy workloads, and one other would possibly help a better throughput for write operations.

40) That are the storage engines utilized by MongoDB?

MMAPv1 and WiredTiger are two storage engines utilized by MongoDB.

41) What’s the utilization of profiler in MongoDB?

A database profiler is used to gather information about MongoDB write operations, cursors, database instructions on a operating MongoDB occasion. You possibly can allow profiling on a per-database or per-instance foundation. The database profiler writes all the info it collects to the system. profile assortment, which is a capped assortment.

42) Is it doable to configure the cache dimension for MMAPv1 in MongoDB?

No. it isn’t doable to configure the cache dimension for MMAPv1 as a result of MMAPv1 doesn’t enable configuring the cache dimension.

43) Learn how to configure the cache dimension for WiredTiger in MongoDB?

For the WiredTiger storage engine, you’ll be able to specify the utmost dimension of the cache that WiredTiger will use for all information. This may be performed utilizing storage.wiredTiger.engineConfig.cacheSizeGB possibility.

44) How does MongoDB present concurrency?

MongoDB makes use of reader-writer locks for concurrency. Reader-writer locks enable concurrent readers shared entry to a useful resource, similar to a database or assortment, however give unique entry to a single write operation.

45) What’s the distinction between MongoDB and Redis databases?

Distinction between MongoDB and Redis:

  • Redis is quicker than MongoDB.
  • Redis has key-value storage whereas MongoDB has document-type storage.
  • Redis is tough to code however MongoDB is straightforward.
46) What’s the distinction between MongoDB and CouchDB?

Distinction between MongoDB and CouchDB:

  • MongoDB is quicker than CouchDB whereas CouchDB is safer than MongoDB.
  • Triggers usually are not obtainable in MongoDB whereas triggers can be found in CouchDB.
  • MongoDB serializes JSON information to BSON whereas CouchDB does not retailer information in JSON format.
47) What’s the distinction between MongoDB and Cassandra?

Distinction between MongoDB and Cassandra:

  • MongoDB is a cross-platform document-oriented database system whereas Cassandra is a excessive efficiency distributed database system.
  • MongoDB is written in C++ whereas Cassandra is written in Java.
  • MongoDB is straightforward to manage within the case of a failure whereas Cassandra supplies excessive availability with no single level of failure.
48) Is there any have to create a database command in MongoDB?

You need not create a database manually in MongoDB as a result of it creates mechanically whenever you save the worth into the outlined assortment on the first time.

MongoDB Interview Questions

The article was published on October 18, 2021 @ 12:21 PM

Leave a Comment