MongoDB Interview Preparation Guide
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MongoDB frequently Asked Questions by expert members with experience in MongoDB. These questions and answers will help you strengthen your technical skills, prepare for the new job test and quickly revise the concepts

39 MongoDB Questions and Answers:

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 documents with dynamic schemas, making the integration of data in certain types of applications easier and faster. Released under a combination of the GNU Affero General Public License and the Apache License, MongoDB is free and open-source software.

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 detail.

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 design and definition, normalization, speed and performance. By comparing MySQL with MongoDB, we are comparing Relational and non-relational databases.

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 they don't share much in common. There are a lot of difference between MongoDB and CouchDB in terms of implementation of their data-model, interface, object storage, replication methods etc.

5 :: Tell me what makes MongoDB best?

Following features of MongoDB make it best NoSQL database:

High performance
High availability
Easy scalability
Rich query language

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 systems.

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 complete.

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 slower than they should be; use this information, for example, to determine when an index is needed.

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 namespace.

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

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