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Technical Architecture

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This diagram outlines the following components and interactions and visualizes the technical architecture to where the model is converted to:

  1. Secrets Manager: Manages sensitive information and can be accessed by the Notifier Lambda function.
  2. Cognito (IAM): Manages user authentication and access permissions.
  3. AppSync (API Gateway): Handles GraphQL API requests and invokes other Lambda functions.
  4. EventBridge: Acts as the event bus, orchestrating events between various Lambda functions.
  5. Lambda Functions:
    • Notifier: Also known as Automations, they may interact with AWS resources, the AppSync API or other API's.
    • T&T (Track & Trace): Processes and stores the trace messages.
    • Projection Engine: Handles data projections.
    • View Updater: Updates the View Store with the latest data.
    • Domain Behavior: Executes the business logic.
      • Triggers: Activate Lambda functions based on specific ActorEvents or DomainEvents.
  6. DynamoDB Tables:
    • Trace Table: Holds trace events.
    • View Store: Contains data for display.
    • IdempotencyStore: Ensures idempotent actions.
    • EventStore: Stores all events.
    • Transactional Outbox: Manages transactional messages that need to be published to EventBridge.

Mutation Workflow

  • AppSync receives GraphQL requests and invokes publishes an ActorEvent on the EventBridge.
  • T&T Lambda registers the request in track and trace.
  • Domain Behavior Lambda
    • IdempotencyStore is checked to ensure the request is not already processed. In case it is a duplicate request, a T&T success/already procesed event is published.
    • EventStore: The state is rehydrated from the event store.
    • business logic is executed
    • The IdempotencyStore, EventStore & Transactional Outbox are updated.
  • T&T Lambda: registers the behavior processing state in track and trace.
  • EventFanout: The DomainEvent(s) are published on the EventBridge.
  • Notifier: An automation may trigger on one of the domain events and take action accordingly. For example: querying the App via AppSync, construct a command, and trigger a new mutation via AppSync (using the same trace id).
  • View Updater Lambda reads snapshots from the Transactional Outbox and updates the View Store.

Query Workflow

AppSync receives GraphQL requests and resolves all statements to DynamoDB queries using VTL scripting. This may invoke numerous DynamoDB queries that will be aggregated into 1 response. This results in fast response times.

Summary

This architecture is designed to be serverless, scalable, and cost-effective, leveraging AWS managed services to minimize operational overhead and focus on application logic and performance.