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MongoDB interview questions

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Question
What kind of database MongoDB is?
Answer
MongoDB is document oriented NOSQL database. Its stores its documents in form of BSON structured documents stored in collection.
Question
Why should we use MongoDB instead of RDB?
Answer
Using or not using MongoDB depends on scope and requirements of app. We should use MongoDB when models need to be modified or extended on the fly and structure of models is not important.

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Question
Does MongoDB support foreign key constraints?
Answer
No.
Question
How does indexing work in MongoDB?
Answer
Indexes are applied to queries which results in read efficiency. If index is created and applied Mongo doesn’t scan every document in collection instead it will look up indexed results achieving read efficiency.
Question
What factors must be kept in account before applying indexes in MongoDB?
Answer
Amount of memory available to system. Ratio of reads to writes. Frequency of query, index is applied to.
Question
What makes indexedDB search fast?
Answer
Indexes are stored in RAM or are stored in sequential memory on disk, this makes this search lot fast such as covered query.
Question
What is the maximum size of MongoDB document?
Answer
16 MB.
Question
How can we use profiler in Mongo DB to achieve efficiency?
Answer
Profiler gives information about performance characteristics of each database operation. This information can be used to identify efficient queries and identifying indexes.
Question
What is Aggregation in MongoDB?
Answer
In MongoDB aggregation is grouping values from multiple documents and running query on grouped data to find results.

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Question
How is Object ID composed in MongoDB?
Answer
3 bytes incremented counter. Client machine id. Time stamp. Client process id.
Question
What sort of schema MongoDB database has?
Answer
MongoDB database has dynamic schema, this means there is no need to define structure for creating collections.
Question
What is sharding in MongoDB?
Answer
Process of storing different data records across more machines is called sharding. This solution is useful in situation of handling more data records and efficient query.
Question
How does MongoDB achieve concurrency?
Answer
MongoDB has read and write locks which grants many users read access at same time but do single write on DB at a time.
Question
What are methods for bulk write in MongoDB?
Answer
Two ways are available here, serial and nonserial write. Serial write will write to DB in order, and if any write fail, all other operations will also stop. In non serial write, order of write is not consistent and execution won’t stop if any write fails.

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