Decouple Domains from Change

[Zhiyuan-Amos]

Create

flowchart TD
    subgraph Issue
    A((Function App)) --> |Write|B(Cosmos DB)
    B --> |Trigger|C(Change Feed)
    D(Change Feed Processor) --> |Read|C
    end
    subgraph Change
    D --> |Write|E(Queue)
    F(Queue Processor) --> |Read|E
    F --> |Write|G(Database)
    end

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For Image, write to Image Outbox and use Change Feed Processor to implement Transactional Outbox pattern and write to

1. Image
2. Storage
3. Change's Queue

Delete

flowchart TD
    subgraph Change
    A((Function App)) --> |Write|B(Cosmos DB)
    B --> |Trigger|C(Change Feed)
    D(Change Feed Processor) --> |Read|C
    end
    subgraph Issue
    D --> |Write|E(Event Grid)
    F(Event Grid Processor) --> |Read|E
    F --> |Delete|G(Database)
    end

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For Image, apart from deleting from database, also delete from Storage

Notes

1. Notice Create uses Queue while Delete uses Event Grid. See Events vs Messages for more information.
2. AuthZ has to be updated - IssueScope, ImageScope, ChangeScope.
3. GetImage & CreateChange are separate Function Apps, protected by Scopes that are not accessible by the Client. (find out how Functions can get the scopes to be authorized to call these other Functions)