Here are some of the most frequently asked MongoDB interview questions and answers.
1. Can you give the definition of MongoDB?
Essentially, MongoDB is nothing but a kind of document database. The chief reasons why it is relevant is due to its good performance ratio and scalability.
2. What do you mean by Namespace and sharding in MongoDB?
Chiefly, the name of the concerned database collection is primarily known as the Namespace. Sharding, on the other hand, is defined as the procedure of storing data across a string of machines. Technically, the data are arranged in a horizontal or linear pattern. Each pattern is referred to as a shard.
3. Can you tell us how to create a Schema in MongoDB?
In order to create a Schema, first and foremost, you need to take the requirements of the user into consideration. In case you wish to use objects combined, blend the objects into a single document. However, it is especially important to keep in mind that such combinations are to be made only in the write mode, not the read mode. If there are a considerable number of use cases, it is better to optimize your Schema and then perform schema aggregation.
4. Can you highlight the precise application of the profiler in MongoDB? Also, what is the purpose of using the moveChunk directory?
As the name suggests, the profiler is essentially meant to reflect the characteristic performance ratio of each and every operation. Moreover, profilers may also be sued in order to file queries.
So far as the moveChunk directory is concerned, it is essentially used for the locomotion of old files. By availing of the sharding process, the old files are temporarily treated as potential back-ups which need not be considered beyond the satisfactory culmination of the operations.
5. What do you think is the chief motto of calling getLastError?
Indeed, the greatest myth regarding the same is that its primary application is the enforced durability of a write. However, the chief motto of calling getLastError is to confirm the successful culmination of a write operation. In fact, it is important to call it in order for the server to correspond accordingly. However, it is important to keep in mind that the durability or safety of the write is independent of the same.
6. What do you think is the approximate time taken by the replica set fall over? Speaking of time, what do you think is the eventuality of a slow sharding?
Normally, it does not take beyond twenty to thirty seconds. It is precisely during the course of these few seconds that the primary is replaced by the declaration of a new primary.
When sharding moves at a retarded pace, the concerned query will return an error statement. They can be deleted only upon the satisfactory completion of the operations.
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7. What do you understand by the terms master and slave?
Typically, master or primary is defined as the present node which is endowed with the task of processing the writes of the replica set. A slave, on the other hand, is a secondary node which applies operations continuing from the present primary or master. The chief characteristic of the slave is to try and remain as congruent with the master as possible.
8. What then do you think are the limitations, if any, of MongoDB?
Indeed, there are limitations. First and foremost, it is important to note that MongoDB is conducive only to limited functionalities such as analytical implementations. Also, it is generally advised to work with a 64 bit MongoDB in order to prevent the corruption of the database after limited operations. Additionally, one of the chief limitations of MongoDB is the representation of data relationships without the construction of clumsy tables.
9. Do you think null values are allowed in MongoDB?
It depends. Null values are only allowed for members of an object. However, it cannot be concatenated to a database collection as it is not an object.
10. What do you understand by the term 32 bit nuances?
So far as the term 32 bit nuances are concerned, it is essentially the amount of the memory space left upon curtailing the extra memory file activity. Precisely, this docking of the memory size is needed in order to achieve a substantial consolidation of the journaling.