From 7d4f1d6cd80cafeef9ff5bbaf06d1f0f2ae6c2be Mon Sep 17 00:00:00 2001
From: heitorlessa <lessa@amazon.co.uk>
Date: Fri, 16 Jun 2023 11:44:42 +0200
Subject: [PATCH] docs(idempotency): new sequence flow when idempotency key is
 optional

---
 docs/utilities/idempotency.md | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/docs/utilities/idempotency.md b/docs/utilities/idempotency.md
index 7bbb279a3e2..4caa91250c8 100644
--- a/docs/utilities/idempotency.md
+++ b/docs/utilities/idempotency.md
@@ -649,6 +649,36 @@ sequenceDiagram
 <i>Idempotent request during and after Lambda timeouts</i>
 </center>
 
+#### Optional idempotency key
+
+<center>
+```mermaid
+sequenceDiagram
+    participant Client
+    participant Lambda
+    participant Persistence Layer
+    alt request with idempotency key
+        Client->>Lambda: Invoke (event)
+        Lambda->>Persistence Layer: Get or set idempotency_key=hash(payload)
+        activate Persistence Layer
+        Note over Lambda,Persistence Layer: Set record status to INPROGRESS. <br> Prevents concurrent invocations <br> with the same payload
+        Lambda-->>Lambda: Call your function
+        Lambda->>Persistence Layer: Update record with result
+        deactivate Persistence Layer
+        Persistence Layer-->>Persistence Layer: Update record
+        Note over Lambda,Persistence Layer: Set record status to COMPLETE. <br> New invocations with the same payload <br> now return the same result
+        Lambda-->>Client: Response sent to client
+    else request(s) without idempotency key
+        Client->>Lambda: Invoke (event)
+        Note over Lambda: Idempotency key is missing
+        Note over Persistence Layer: Skips any operation to fetch, update, and delete
+        Lambda-->>Lambda: Call your function
+        Lambda-->>Client: Response sent to client
+    end
+```
+<i>Optional idempotency key</i>
+</center>
+
 ## Advanced
 
 ### Persistence layers