MongoDB Interview Questions:

What are some advantages of MongoDB?
- Supports field, range-based, and string pattern matching queries
- Primary and secondary index support
- Uses JavaScript objects instead of procedures
- Dynamic database schema
- Easy scalability
- Built-in support for data partitioning (Sharding)

What is a Document in MongoDB?
- Ordered set of keys with associated values
- Represented as a map, hash, or dictionary
- Example: {"greeting": "Hello world!", "views": 3}

What is a Collection in MongoDB?
- Group of documents
- Analogous to a table in relational databases
- Collections have dynamic schemas

What are Databases in MongoDB?
- Group collections into databases
- MongoDB can host several databases
- Reserved database names include admin, local, config

What is the Mongo Shell?
- JavaScript shell for interacting with MongoDB from the command line
- Used for administrative functions, inspecting instances, and exploring MongoDB
- Full-featured JavaScript interpreter

How does Scale-Out occur in MongoDB?
- Document-oriented model makes it easy to split data across multiple servers
- MongoDB balances and loads data across a cluster automatically
- Mongos acts as a query router
- Config servers store metadata and configuration settings

What are some features of MongoDB?
- Indexing support
- Aggregation framework
- Special collection and index types (e.g., TTL collections)
- File storage
- Sharding for horizontal scaling

How to add data in MongoDB?
- Use inserts, insertOne for single document, insertMany for multiple documents

How do you Update a Document?
- Use updateOne, updateMany, or replaceOne methods
- Provide filter document and modifier document for updates

How do you Delete a Document?
- Use deleteOne or deleteMany methods
- Specify a filter document to match against documents to be removed

How to perform queries in MongoDB?
- Use the find method
- Query criteria specified by a document

What are the data types in MongoDB?
- Null
- Boolean
- Number
- String
- Date
- Regular expression
- Array
- Embedded document
- Object ID
- Binary data
- Code

When to use MongoDB?
- Rapid iterative development
- Scaling to high levels of read and write traffic
- Scaling data repository to a massive size
- Evolving deployment as business changes
- Storing, managing, and searching data with various dimensions

How is Querying done in MongoDB?
- Use the find method
- Query criteria specified by a document

Explain the term “Indexing” in MongoDB.
- Indexes help efficiently resolve queries
- Stores a small part of the data set in an easily traversable form
- Create indexes using createIndex method

What are Geospatial Indexes in MongoDB?
- Two types: 2dsphere and 2d
- 2dsphere for spherical geometries based on the WGS84 datum
- 2d for points on a two-dimensional plane

Explain the process of Sharding.
- Splitting data across machines
- Create a cluster of many machines (shards) and break up a collection across them
- Each shard stores a subset of data

Explain the SET Modifier in MongoDB?
- Sets the value of a field if it doesn't exist
- Useful for updating schemas or adding user-defined keys

What do you mean by Transactions?
- Logical unit of processing including one or more database operations
- Ensures consistency in MongoDB
- Core API or Call-back API can be used

What are MongoDB Charts?
- Integrated tool for data visualization in MongoDB
- Offers a way to create visualizations using data from a MongoDB database
- Two implementations: MongoDB Charts PaaS and MongoDB Charts Server

What is the Aggregation Framework in MongoDB?
- Set of analytics tools for performing analytics on documents
- Based on the concept of a pipeline
- Documents pass through stages, each performing a different operation

Explain the concept of pipeline in the MongoDB aggregation framework.
- Individual stage of data processing unit
- Processes documents one at a time and produces output stream
- Documents pass through stages sequentially

What is a Replica Set in MongoDB?
- Group of servers with one primary and multiple secondaries
- Primary receives write operations, secondaries keep copies of primary's data
- Ensures high availability and data safety

Explain the Replication Architecture in MongoDB.
- Primary receives write operations and saves data changes in the Oplog
- Secondaries query primary for new changes in the Oplog and copy them
- Changes applied from Oplog to secondaries' datafiles

What are some utilities for backup and restore in MongoDB?
- mongoimport
- mongoexport
- mongodump
- mongorestore