Exam DP-420 topic 3 question 3 discussion

HOTSPOT -
You have three containers in an Azure Cosmos DB Core (SQL) API account as shown in the following table.

You have the following Azure functions:
✑ A function named Fn1 that reads the change feed of cn1
✑ A function named Fn2 that reads the change feed of cn2
✑ A function named Fn3 that reads the change feed of cn3
You perform the following actions:
✑ Delete an item named item1 from cn1.
✑ Update an item named item2 in cn2.
✑ For an item named item3 in cn3, update the item time to live to 3,600 seconds.
For each of the following statements, select Yes if the statement is true. Otherwise, select No.
NOTE: Each correct selection is worth one point.
Hot Area:

Suggested Answer:
Box 1: No -
Azure Cosmos DB's change feed is a great choice as a central data store in event sourcing architectures where all data ingestion is modeled as writes (no updates or deletes).
Note: The change feed does not capture deletes. If you delete an item from your container, it is also removed from the change feed. The most common method of handling this is adding a soft marker on the items that are being deleted. You can add a property called "deleted" and set it to "true" at the time of deletion. This document update will show up in the change feed. You can set a TTL on this item so that it can be automatically deleted later.

Box 2: No -
The _etag format is internal and you should not take dependency on it, because it can change anytime.

Box 3: Yes -
Change feed support in Azure Cosmos DB works by listening to an Azure Cosmos container for any changes.
Reference:
https://docs.microsoft.com/en-us/azure/cosmos-db/sql/change-feed-design-patterns https://docs.microsoft.com/en-us/azure/cosmos-db/change-feed