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

Recall & Review

beginner

What is a change stream in MongoDB?

A change stream is a feature in MongoDB that lets applications listen for real-time changes (like inserts, updates, deletes) happening in the database without polling.

beginner

How do you start watching a change stream on a MongoDB database?

You use the watch() method on the database object to open a change stream that listens to all changes in that database.

intermediate

Which MongoDB operation types can change streams detect?

Change streams can detect insert, update, replace, delete, and invalidate operations.

intermediate

What is the purpose of the resumeToken in change streams?

The resumeToken lets you restart a change stream from a specific point if the stream is interrupted, so you don't miss any changes.

intermediate

Can change streams be used on a single collection, a database, and the entire cluster?

Yes, change streams can be opened on a single collection, on a whole database, or on the entire MongoDB cluster to watch all changes.

What method do you call to start a change stream on a MongoDB database?

A watch()

B listen()

C subscribe()

D observe()

The watch() method is used to open a change stream on a database or collection.

Which of these operations will NOT trigger a change stream event?

A createIndexes

B insert

C update

D delete

Creating an index does not trigger change stream events; only data changes like insert, update, replace, delete, and invalidate do.

What does the resumeToken help with in change streams?

A Filtering events

B Restarting the stream from a saved point

C Encrypting data

D Sorting change events

The resumeToken allows resuming a change stream from where it left off after an interruption.

Can change streams be used to watch changes across all collections in a database?

A Only on system collections

B No, only on single collections

C Yes, by opening a change stream on the database

D Only on the cluster level

Opening a change stream on a database watches changes across all its collections.

Which MongoDB feature allows applications to react instantly to data changes without polling?

A Sharding

B Aggregation pipeline

C Indexes

D Change streams

Change streams provide real-time notifications of data changes without needing to poll the database.

Explain what a MongoDB change stream is and how it can be used in an application.

Think about how apps get notified instantly when data changes.

Describe the different levels at which you can open a change stream in MongoDB and what each level watches.

Consider the scope of changes you want to monitor.