Change streams on collections in MongoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a change stream in MongoDB?

A change stream lets you watch real-time changes (like inserts, updates, deletes) happening in a MongoDB collection or database.

beginner

How do you start watching changes on a MongoDB collection?

You use the watch() method on the collection object to open a change stream cursor.

intermediate

What kind of operations can change streams detect?

Change streams detect inserts, updates, deletes, replaces, and sometimes drops or renames on collections.

beginner

Why are change streams useful in real-life applications?

They help apps react instantly to data changes, like updating a live dashboard or syncing data between services.

intermediate

What is the role of the resumeToken in change streams?

The resumeToken lets you restart watching from where you left off if the stream disconnects.

Which MongoDB method starts a change stream on a collection?

A find()

B aggregate()

C watch()

D update()

The watch() method opens a change stream cursor on a collection.

What type of changes can a change stream NOT detect?

A Inserts

B Client-side variable changes

C Deletes

D Updates

Change streams only detect database changes, not client-side variable changes.

What does the resumeToken help with in change streams?

A Restarting the stream after disconnect

B Starting a new database

C Deleting documents

D Creating indexes

The resumeToken allows resuming the change stream from the last seen event.

Which of these is a common use case for change streams?

A Static report generation

B Batch data import

C Manual data entry

D Real-time notifications

Change streams enable real-time notifications by watching data changes as they happen.

Can change streams watch changes across multiple collections at once?

A Yes, by watching the whole database

B No, only one collection at a time

C Only if collections are in different databases

D Only for system collections

You can watch changes across all collections in a database by opening a change stream on the database.

Explain how to use change streams to monitor real-time changes in a MongoDB collection.

Think about opening a stream and reacting to events as they come.

Describe practical scenarios where change streams can improve an application.

Consider apps that need instant data awareness.