AWS powertools documentation change

Service: powertools · 2026-07-13 · Documentation low

File: powertools/typescript/latest/features/event-handler/appsync-events.md

Summary

Added documentation for detecting oversized AppSync events exceeding 240KB limit and added links to Data Masking/Signer features

Security assessment

The change adds observability for oversized events but doesn't address a specific security vulnerability. The warning feature helps debug message delivery issues but doesn't mitigate security risks.

Diff

diff --git a/powertools/typescript/latest/features/event-handler/appsync-events.md b/powertools/typescript/latest/features/event-handler/appsync-events.md
index 90eb3fc88..8829bd924 100644
--- a//powertools/typescript/latest/features/event-handler/appsync-events.md
+++ b//powertools/typescript/latest/features/event-handler/appsync-events.md
@@ -57,0 +58 @@ Event Handler
+            * Detecting oversized events 
@@ -77,0 +79 @@ Event Handler
+      * [ Data Masking  ](../../data-masking/)
@@ -78,0 +81 @@ Event Handler
+      * [ Signer  ](../../signer/)
@@ -112,0 +116 @@ Table of contents
+    * Detecting oversized events 
@@ -994,0 +999,51 @@ Aggregated processing with partial results
+### Detecting oversized events¶
+
+AWS AppSync Events limits each event to a [maximum size of 240 KB](https://docs.aws.amazon.com/appsync/latest/eventapi/event-api-concepts.html), including its `id`. Events larger than this limit are silently dropped by AppSync and never delivered to subscribers, which can be hard to diagnose.
+
+You can enable the `warnOnLargePayload` option to emit a warning log whenever an individual event in your response exceeds this limit. To avoid log spam, the warning is emitted at most once per channel path.
+
+Warning on oversized events
+    
+    
+     1
+     2
+     3
+     4
+     5
+     6
+     7
+     8
+     9
+    10
+    11
+    12
+    13
+    14
+    15
+    16
+
+| 
+    
+    
+    import { AppSyncEventsResolver } from '@aws-lambda-powertools/event-handler/appsync-events';
+    import type { Context } from 'aws-lambda';
+    
+    const app = new AppSyncEventsResolver({
+      warnOnLargePayload: true,
+    });
+    
+    app.onPublish('/default/foo', (payload) => {
+      return {
+        processed: true,
+        original_payload: payload,
+      };
+    });
+    
+    export const handler = async (event: unknown, context: Context) =>
+      app.resolve(event, context);
+      
+  
+---|---  
+  
+This option is disabled by default because measuring the size requires serializing each event in the response, which has a performance cost on large batches. Enable it while you investigate dropped messages, or keep it on if the overhead is acceptable for your workload.
+
@@ -1956 +2011 @@ Testing subscribe eventsSample subscribe event
-2026-05-27 
+2026-07-10