Top MongoDB Interview Questions and Answers
MongoDB is a cross-platform document-based database. Categorized as a NoSQL database, MongoDB avoids the conventional table-oriented relational database structure in support of the JSON-like documents with the dynamic schemas, making the data integration in specific kinds of applications quicker and simpler.
MongoDB was developed by a software company “10gen”, in October 2007 as an element of the planned platform as the service product. After that, the company was shifted to a freeware deployment model in 2009, providing sales assistance and other services.
How to add data in MongoDB?
The basic method for adding data to MongoDB is “inserts”. To insert a single document, use the collection’s insertOne method:
For inserting multiple documents into a collection, we use insertMany. This method enables passing an array of documents to the database.
31) How can MongoDB simulate subquery or join?
We have to find the best method for structuring the data in MongoDB for simulating what would be the simple subquery or join in SQL. For example, we have users and posts, with the users in one collection and posts in another collection. We have to find all the posts by the users whose city is “Hyderabad”.
An operational log (oplog) is a special kind of limited collection that stores a rolling record of all the operations which change the data we store in our databases. Primarily, it applies all the database operations over the primary and, after that, records these operations on the oplog of the primary. After that, the secondary members replicate and apply the operations in the asynchronous process.
What are some of the advantages of MongoDB?
Some advantages of MongoDB are as follows:
When and to what extent does data get extended to multi-slice?
MongoDB scrap stands on a collection. So, an album of all substances is kept in a lump or mass. Only when there is an additional time slot, there will be more than a few slice data achievement choices, but when there is more than one lump, data gets extended to a lot of slices and it can be extended to 64 MB.
Download PDF Your requested download is ready! Click
MongoDB groups collections into databases. MongoDB can host several databases, each grouping together collections. Some reserved database names are as follows:adminlocalconfig
36) Which command do we use for creating the backup of the database?
We use the mongodump command for creating the database backup.
2 Explain Replication.
Replication is the process of synchronizing data across multiple servers.
70) How do applications access the real-time data modifications in MongoDB?
Applications access the real-time data modifications through the Change streams that serve as the subscriber for every collection operation like delete, insert, and update.
Compare MongoDB with Cassandra.
Learn about a brief comparison between MongoDB and Cassandra using this table.
| Criteria | MongoDB | Cassandra |
| Data Model | Document | Bigtable like |
| Database scalability | Read | Write |
| Querying of data | Multi-indexed | Using Key or Scan |
To have a detailed comparison between MongoDB and Cassandra, check out Cassandra Versus MongoDB!
1 What is CRUD?
MongoDB provides CRUD operations:
Click here to learn more about MongoDB CRUD Operations in our MongoDB Tutorial!