What is MongoDB?
Mongo-DB is a document database which provides high performance, high availability and easy scalability.
What is “Namespace” in MongoDB?
MongoDB stores BSON (Binary Interchange and Structure Object Notation) objects in the collection. The concatenation of the collection name and database name is called a namespace.
What is sharding in MongoDB?
The procedure of storing data records across multiple machines is referred as Sharding. It is a MongoDB approach to meet the demands of data growth. It is the horizontal partition of data in a database or search engine. Each partition is referred as shard or database shard.
What are NoSQL databases? What are the different types of NoSQL databases?
A NoSQL database provides a mechanism for storage and retrieval of data that is modeled in means other than the tabular relations used in relational databases (like SQL, Oracle, etc.).
Types of NoSQL databases:
  • Key value store NoSQL database
  • Document store NoSQL database
  • Column store NoSQL database
  • Graph base NoSQL database
What kind of NoSQL database MongoDB is?
MongoDB is a document oriented database. It stores data in the form of BSON structure based documents. These documents are stored in a collection.
What is the difference between MongoDB and MySQL?
Although MongoDB and MySQL both are free and open source databases, there is a lot of difference between them in the term of data representation, relationship, 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.
Why MongoDB is known as best NoSQL database?
MongoDB is the best NoSQL database because, it is:
  • Document Oriented
  • Rich Query language
  • High Performance
  • Highly Available
  • Easily Scalable
What is the difference b/w MongoDB and CouchDB?
MongoDB and CouchDB both are the great example of open source NoSQL database. both are document oriented databases. Although both stores data but there is a lot of difference between them in terms of implementation of their data models, interfaces, object storage and replication methods etc.
What is a Namespace in MongoDB?
Namespace is a concatenation of the database name and the collection name. Collection, in which MongoDB stores BSON objects.
Which languages can be used with MongoDB?
Currently, MongoDB provides official driver support for C, C++, C#, Java, Node.js, Perl, PHP, Python, Ruby, Scala, Go and Erlang. MongoDB can easily be used with any of these languages. There are some other community supported drivers too but the above mentioned ones are officially provided by MongoDB.
How is MongoDB better than other SQL databases?
MongoDB allows a highly flexible and scalable document structure. For e.g. one data document in MongoDB can have five columns and the other one in the same collection can have ten columns. Also, MongoDB database are faster as compared to SQL databases due to efficient indexing and storage techniques.
Does MongoDB support foreign key constraints?
No. MongoDB does not support such relationships.
Does MongoDB need a lot of RAM?
No. MongoDB can be run even on a small amount of RAM. MongoDB dynamically allocates and de-allocates RAM based on the requirements of other processes.
Explain the structure of ObjectID in MongoDB.
ObjectID is a 12-byte BSON type with:
  • 4-bytes value representing seconds
  • 3-byte machine identifier
  • 2-byte process id
  • 3-byte counter
What are Indexes in MongoDB?
Indexes support the efficient execution of queries in MongoDB. Without indexes, MongoDB must perform a collection scan, i.e. scan every document in a collection, to select those documents that match the query statement. If an appropriate index exists for a query, MongoDB can use the index to limit the number of documents it must inspect.
What is a covered query in MongoDB?
A covered query is the one in which:
  • fields used in the query are part of an index used in the query, and
  • the fields returned in the results are in the same index
Why is a covered query important?
Since all the fields are covered in the index itself, MongoDB can match the query condition as well as return the result fields using the same index without looking inside the documents. Since indexes are stored in RAM or sequentially located on disk, such access is a lot faster.
What is Aggregation in MongoDB?
Aggregations operations process data records and return computed results. Aggregation operations group values from multiple documents together, and can perform a variety of operations on the grouped data to return a single result. MongoDB provides three ways to perform aggregation: the aggregation pipeline, the map-reduce function, and single purpose aggregation methods and commands.
What is Sharding in MongoDB?
Sharding is a method for storing data across multiple machines. MongoDB uses sharding to support deployments with very large data sets and high throughput operations.
What is Replication in MongoDB?
Replication is the process of synchronizing data across multiple servers. Replication provides redundancy and increases data availability. With multiple copies of data on different database servers, replication protects a database from the loss of a single server. Replication also allows you to recover from hardware failure and service interruptions.
What are Primary and Secondary Replica sets?
Primary and master nodes are the nodes that can accept writes. MongoDB's replication is 'single-master:' only one node can accept write operations at a time.
Secondary and slave nodes are read-only nodes that replicate from the primary.
Why are MongoDB data files large in size?
MongoDB preallocates data files to reserve space and avoid file system fragmentation when you setup the server.
Why MongoDB is not preferred over a 32-bit system?
When running a 32-bit build of MongoDB, the total storage size for the server, including data and indexes, is 2 gigabytes. For this reason, do not deploy MongoDB to production on 32-bit machines.
If you're running a 64-bit build of MongoDB, there's virtually no limit to storage size.
What is a Storage Engine in MongoDB?
A storage engine is the part of a database that is responsible for managing how data is stored on disk. For example, one storage engine might offer better performance for read-heavy workloads, and another might support a higher-throughput for write operations.
What is GridFS in MongoDB?
For storing and retrieving large files such as images, video files and audio files GridFS is used. By default, it uses two files fs.files and fs.chunks to store the file’s metadata and the chunks.
What are alternatives to MongoDB?
Cassandra, CouchDB, Redis, Riak, HBase are a few good alternatives.
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