Mongodb Interview Questions And Answers

Mongodb Interview Questions list for experienced

  1. What is MongoDB?
  2. Explain what are the various types of NoSQL databases?
  3. Explain what is the basic difference between MySQL and MongoDB?
  4. Please compare MongoDB with CouchDB and CouchBase?
  5. Tell me what makes MongoDB best?
  6. Do you know what is 32 bit nuances?
  7. Tell me will the journal replay have problems if entries are incomplete (like the failure happened in the middle of one)?
  8. What is role of Profiler in MongoDB?
  9. What is a \"namespace\"?
  10. Suppose if you remove an object attribute is it deleted from the store?
  11. Explain are null values allowed?
  12. Does an update fsync to disk immediately?
  13. How to do transactions/locking?
  14. Tell me why are my data files so large?
  15. Explain how long does replica set failover take?
  16. What is a master or primary?
  17. What is a secondary or slave?
  18. Explain do I have to call getLastError to make a write durable?
  19. Tell me should I start out with sharded or with a non-sharded MongoDB environment?
  20. Explain how does sharding work with replication?
  21. Tell me when will data be on more than one shard?
  22. Explain what happens if I try to update a document on a chunk that is being migrated?
  23. Explain what if a shard is down or slow and I do a query?
  24. Tell me can I remove old files in the moveChunk directory?
  25. How to see the connections used by mongos?
  26. Explain if a moveChunk fails do I need to cleanup the partially moved docs?
  27. What types of 2 NoSQL database?
  28. Explain what is the basic difference between 3 MySQL and MongoDB?
  29. How do you compareMongoDB, CouchDB and CouchBase?
  30. What are the subtle distinction between the 32 bit system?
  31. What is the role of analyzer in MongoDB?

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Top Mongodb interview questions and answers for freshers and experienced

What is Mongodb ?

Answer : MongoDB is a scalable, high-performance, open source, document-oriented database. It supports a large number of languages and application development platforms.

Questions : 1 :: What is MongoDB?

MongoDB is a cross-platform document-oriented database. Classified as a NoSQL database, MongoDB eschews the traditional table-based relational database structure in favor of JSON-like...View answers

Questions : 2 :: Explain what are the various types of NoSQL databases?

Examples: MongoDB, Cassandra, CouchDB, Hypertable, Redis, Riak, Neo4j, HBASE, Couchbase, MemcacheDB, RevenDB and Voldemort are the examples of NoSQL databases. Read in...View answers

Questions : 3 :: Explain what is the basic difference between MySQL and MongoDB?


MySQL and MongoDB are both free and open source databases. MySQL and MongoDB have a lot of basic differences in terms of data representation, querying, relationships, transactions, schema...View answers

Questions : 4 :: Please compare MongoDB with CouchDB and CouchBase?

MongoDB and CouchDB are both document-oriented databases. MongoDB and CouchDB are the best examples of open source NoSQL database. Aside from both storing documents though, it turns out that...View answers

Questions : 5 :: Tell me what makes MongoDB best?

Following features of MongoDB make it best NoSQL database:Document-orientedHigh performanceHigh availabilityEasy scalabilityRich query...View answers

Questions : 6 :: Do you know what is 32 bit nuances?


There is extra memory mapped file activity with journaling. This will further constrain the limited db size of 32 bit builds. Thus, for now journaling by default is disabled on 32 bit...View answers

Questions : 7 :: Tell me will the journal replay have problems if entries are incomplete (like the failure happened in the middle of one)?

Each journal (group) write is consistent and won't be replayed during recovery unless it is...View answers

Questions : 8 :: What is role of Profiler in MongoDB?

MongoDB includes a database profiler which shows performance characteristics of each operation against the database. Using the profiler you can find queries (and write operations) which are...View answers

Questions : 9 :: What is a "namespace"?


MongoDB stores BSON objects in collections. The concatenation of the database name and the collection name (with a period in between) is called a...View answers

Questions : 10 :: Suppose if you remove an object attribute is it deleted from the store?

Yes, you remove the attribute and then re-save() the...View answers

Questions : 11 :: Explain are null values allowed?

For members of an object, yes. You cannot add null to a database collection though as null isn't an object. You can add {},...View answers

Questions : 12 :: Does an update fsync to disk immediately?

No, writes to disk are lazy by default. A write may hit disk a couple of seconds later. For example, if the database receives a thousand increments to an object within one second, it will...View answers

Questions : 13 :: How to do transactions/locking?

MongoDB does not use traditional locking or complex transactions with rollback, as it is designed to be lightweight and fast and predictable in its performance. It can be thought of as...View answers

Questions : 14 :: Tell me why are my data files so large?

MongoDB does aggressive preallocation of reserved space to avoid file system...View answers

Questions : 15 :: Explain how long does replica set failover take?

it may take 10-30 seconds for the primary to be declared down by the other members and a new primary elected. During this window of time, the cluster is down for "primary" operations...View answers

Questions : 16 :: What is a master or primary?

This is a node/member which is currently the primary and processes all writes for the replica set. In a replica set, on a failover event, a different member can become...View answers

Questions : 17 :: What is a secondary or slave?

A secondary is a node/member which applies operations from the current primary. This is done by tailing the replication oplog (local.oplog.rs).Replication from primary to secondary is...View answers

Questions : 18 :: Explain do I have to call getLastError to make a write durable?

No. If you don't call getLastError (aka "Safe Mode") the server does exactly the same behavior as if you had. The getLastError call simply lets one get confirmation that the write...View answers

Questions : 19 :: Tell me should I start out with sharded or with a non-sharded MongoDB environment?

We suggest starting unsharded for simplicity and quick startup unless your initial data set will not fit on single servers. Upgrading to sharding from unsharded is easy and seamless, so there...View answers

Questions : 20 :: Explain how does sharding work with replication?

Each shard is a logical collection of partitioned data. The shard could consist of a single server or a cluster of replicas. We recommmend using a replica set for each...View answers

Questions : 21 :: Tell me when will data be on more than one shard?

MongoDB sharding is range based. So all the objects in a collection get put into a chunk. Only when there is more than 1 chunk is there an option for multiple shards to get data. Right now,...View answers

Questions : 22 :: Explain what happens if I try to update a document on a chunk that is being migrated?

The update will go through immediately on the old shard, and then the change will be replicated to the new shard before ownership...View answers

Questions : 23 :: Explain what if a shard is down or slow and I do a query?

If a shard is down, the query will return an error unless the "Partial" query options is set. If a shard is responding slowly, mongos will wait for...View answers

Questions : 24 :: Tell me can I remove old files in the moveChunk directory?

Yes, these files are made as backups during normal shard balancing operations. Once the operations are done then they can be deleted. The cleanup process is currently manual so please do take...View answers

Questions : 25 :: How to see the connections used by mongos?

...View answers

Questions : 26 :: Explain if a moveChunk fails do I need to cleanup the partially moved docs?

No, chunk moves are consistent and deterministic; the move will retry and when completed the data will only be on the new...View answers

Questions : 27 :: What types of 2 NoSQL database?

For example: MongoDB, Cassandra, CouchDB, Hypertable, Redis, Riak, Neo4j, HBASE, Couchbase, MemcacheDB, RevenDB and Voldemort are the examples of NoSQL...View answers

Questions : 28 :: Explain what is the basic difference between 3 MySQL and MongoDB?

Both MySQL and MongoDB are free open source database. MySQL and MongoDB have many fundamental differences including data representation (data representation), query, relationship, business,...View answers

Questions : 29 :: How do you compareMongoDB, CouchDB and CouchBase?

MongoDB and CouchDB are document oriented database. MongoDB and CouchDB are the most typical representative of the open source NoSQL database. They have nothing in common other than are...View answers

Questions : 30 :: What are the subtle distinction between the 32 bit system?

Journaling activates the memory mapped file additional. This will further suppress the size of the database is a 32 bit version. Therefore, journaling is now the 32 bit system is disabled by...View answers

Questions : 31 :: What is the role of analyzer in MongoDB?

MongoDB includes a display the operating property database each database analyzer. Through this analyzer you can find the slower than expected query (or write); using this information, for...View answers
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