面试题与答案

Indexing is the process of creating an index (like in a book) to improve the performance of queries. Indexes are used to quickly locate and access the data.

Sharding is the process of distributing data across multiple servers. It is MongoDB's approach to meeting the demands of data growth.

Replication is the process of synchronizing data across multiple servers. It provides redundancy and increases data availability.

The profiler is a MongoDB feature that tracks queries executed against the database. It helps in analyzing and optimizing query performance.

MongoDB provides the `aggregate` method to perform aggregation operations, such as filtering, grouping, sorting, and projecting data.

GridFS is a specification for storing and retrieving large files in MongoDB. It divides a file into chunks and stores each chunk as a separate document.

The TTL index is a special type of index that automatically deletes documents from a collection after a specified amount of time has passed.

MongoDB achieves high availability through replica sets, where data is replicated across multiple servers. If one server goes down, another can serve the data.

WiredTiger is the default storage engine in MongoDB. It provides features like compression, document-level locking, and support for multiple storage engines in the same MongoDB deployment.

The Journal in MongoDB is a write-ahead log that helps in recovering data in case of a server crash or failure. It ensures data durability and consistency.

Data migration in MongoDB involves transferring data from one database or collection to another. It can be done using tools like `mongodump` and `mongorestore`.

You can create an index in MongoDB using the `createIndex` method. For example, `db.collection.createIndex({ field: 1 })` creates an ascending index on the specified field.

The `mongorestore` command is used to restore MongoDB backups created with `mongodump`. It imports BSON data into a MongoDB database.