Capped collections for fixed-size data in MongoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a capped collection in MongoDB?

A capped collection is a fixed-size collection that maintains insertion order and automatically overwrites the oldest documents when it reaches its size limit.

beginner

How do you create a capped collection with a maximum size of 1MB in MongoDB?

Use the command: <br>db.createCollection('myCapped', { capped: true, size: 1048576 })<br>This creates a capped collection named 'myCapped' with a size limit of 1 megabyte.

beginner

What happens when a capped collection reaches its size limit?

When the capped collection reaches its size limit, MongoDB automatically overwrites the oldest documents with new ones, preserving the insertion order.

intermediate

Can you delete documents individually from a capped collection?

No, individual document deletion is not allowed in capped collections. You can only insert new documents, and old ones are overwritten automatically when the size limit is reached.

intermediate

Why are capped collections useful for fixed-size data?

They are useful because they provide high-performance inserts and maintain a fixed storage size, making them ideal for logging, caching, or real-time data streams where only recent data is needed.

What is a key feature of a capped collection in MongoDB?

A It automatically overwrites oldest documents when full

B It allows unlimited growth without size limits

C It supports individual document deletion

D It stores data in random order

Capped collections have a fixed size and overwrite the oldest documents automatically when they reach their size limit.

How do you specify a capped collection size when creating it?

A Using the 'max' option

B Using the 'capacity' option

C Using the 'limit' option

D Using the 'size' option in bytes

The 'size' option specifies the maximum size in bytes for the capped collection.

Which operation is NOT allowed on capped collections?

A Inserting new documents

B Querying documents in insertion order

C Deleting individual documents

D Automatically overwriting old documents

Individual document deletion is not allowed in capped collections.

What is a common use case for capped collections?

A Logging and caching recent data

B Storing large archival data

C Storing user profiles

D Running complex transactions

Capped collections are ideal for logging and caching where only recent data is important.

If you want a capped collection to hold a maximum of 1000 documents, what else must you specify?

A The 'limit' option

B The 'max' option along with 'capped: true'

C Only the 'size' option

D No additional options needed

You can specify the maximum number of documents using the 'max' option when creating a capped collection.

Explain what a capped collection is and why it is useful for fixed-size data.

Think about a collection that never grows beyond a set size and keeps only the newest data.

Describe how to create a capped collection in MongoDB and what options you need to set.

Focus on the command and the key options to limit size and documents.