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Interviews / Databases / What is GridFS and when would you use it in MongoDB?

Questions

What is the difference between SQL and NoSQL databases?
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What is the `ObjectId` and what is it used for in MongoDB?
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What is GridFS and when would you use it in MongoDB?
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What are capped collections and when would you use them in MongoDB?
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How do you do data modeling in MongoDB?
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What are indexes and how do they work in MongoDB?
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What is the difference between a sparse and a partial index in MongoDB?
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What is the aggregation framework and how do you use it in MongoDB?
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How do you do replication in MongoDB?
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How do you do sharding in MongoDB?
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What are transactions and how do you use them in MongoDB?
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What is the `explain()` method and what is it used for in MongoDB?
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What is GridFS and when would you use it in MongoDB?

conceptual Core Concepts Interactive Quiz Code Examples

The Scenario

You are a backend engineer at a social media company. You are building a new service that needs to store large files, such as images and videos.

You are considering using either the file system or GridFS to store the files.

The Challenge

Explain what GridFS is in MongoDB and why it is a better choice than the file system for storing large files. What are the key benefits of using GridFS?

Wrong Approach

A junior engineer might try to store the large files in a `BSON` document. This would not work, because `BSON` documents have a size limit of 16MB. They might not be aware of GridFS, which is the correct tool for this job.

Right Approach

A senior engineer would know that GridFS is the perfect tool for this job. They would be able to explain what GridFS is and how to use it to store and retrieve large files. They would also be able to explain the benefits of using GridFS over the file system.

Step 1: Understand What GridFS Is

GridFS is a specification for storing and retrieving large files in MongoDB. It works by dividing a large file into smaller chunks and storing each chunk as a separate document.

Step 2: The fs.files and fs.chunks Collections

GridFS uses two collections to store the files:

CollectionDescription
fs.filesStores the metadata for the files, such as the file name, the content type, and the length.
fs.chunksStores the chunks of the files.

The Benefits of Using GridFS

BenefitDescription
ScalabilityGridFS can be used to store files that are larger than the 16MB BSON document size limit.
ReplicationGridFS files are automatically replicated across the nodes in a replica set.
ShardingGridFS files are automatically sharded across the shards in a sharded cluster.

When to Use GridFS

You should use GridFS when you need to store files that are larger than the 16MB BSON document size limit.

You should not use GridFS if you need to perform atomic updates on the content of a file.

Practice Question

You are building a service that needs to store and retrieve large video files. Which of the following would be the most appropriate?