Organization CQRS doc

Author: beebeb

Course6/index.md

@@ -14,28 +14,33 @@ R
 1. API composition
 2. Dedicated data view
 
+## How to keep data syncronized crossing services
 
-OrderHistoryService
+Let's assume OrderHistoryService as a dedicated database-ElasticSearch which needs all data related to order from other services.
 
-handler  -> order.created
-         -> customer.updated
-         -> ...
 
-ElasticSearch
+OrderHistoryEventHandler subscripes domain events published by MessageQueue
+```
+    -> order.created
+    -> customer.updated
+    -> ...
+```
 
 
 ### Issues
 
-1. Handle duplicated messages
-    1.1 
+* Handle duplicated messages
+    * 1.1 
+    ```
         PROCESSED_EVENT table
         eventId
         maxEventId
-    1.2 
-        幂等性
-
-## API Gateway
+    ```
+    * 1.2 
+        idempotent(幂等性)
 
+## What is API Gateway? 
+ 
 1. API composition
 2. Edge function(Authentication, Authorization, Rate limit, Monitor)
 3. Proxy