From 33dfb27c3a3d0798469ea3425567b17fd88b74ea Mon Sep 17 00:00:00 2001
From: Luca Cucchetti <luca.f.cucchetti@gmail.com>
Date: Sat, 17 Aug 2024 10:01:36 +0100
Subject: [PATCH] DDB Stream read throttling advice

---
 lambda-esm-ddb-filters-sam/README.md          |  5 ++
 .../example-pattern.json                      | 58 +++++++++++++++++++
 2 files changed, 63 insertions(+)
 create mode 100644 lambda-esm-ddb-filters-sam/example-pattern.json

diff --git a/lambda-esm-ddb-filters-sam/README.md b/lambda-esm-ddb-filters-sam/README.md
index 3a74663cb..85cb25b9a 100644
--- a/lambda-esm-ddb-filters-sam/README.md
+++ b/lambda-esm-ddb-filters-sam/README.md
@@ -2,6 +2,11 @@
 
 This pattern demonstrates the ability to filter Amazon DynamoDB Stream events so that only a subset of all events is sent to an AWS Lambda function for processing. Demo stack will create a single Amazon DynamoDB Table (table-lambda-esm-filter), enable [Change Data Capture](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Streams.html) for that table, and create a number of AWS Lambda functions that are subscribed to the Amazon DynamoDB stream using different filter configurations.
 
+> Please note that this template is meant to be for testing the filters, you can subscribe more than two Lambda functions to a DynamoDB Stream, but you'll likely experience [read throttling](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Streams.Lambda.html).
+> 
+> If you require more than two consumers ([one if it is a global table](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ServiceQuotas.html#limits-dynamodb-streams)), consider integrating with [Amazon EventBridge](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/eventbridge-for-dynamodb.html).
+
+
 Review [Filter rule syntax](https://docs.aws.amazon.com/lambda/latest/dg/invocation-eventfiltering.html#filtering-syntax) for more details on the message filtering configuration.
 **Important note**: Filter definition should not contain any whitespace (tabs, space, etc.) in order to work properly!
 
diff --git a/lambda-esm-ddb-filters-sam/example-pattern.json b/lambda-esm-ddb-filters-sam/example-pattern.json
new file mode 100644
index 000000000..e03ca3dca
--- /dev/null
+++ b/lambda-esm-ddb-filters-sam/example-pattern.json
@@ -0,0 +1,58 @@
+{
+  "title": "AWS Event Source Mapping for Lambda from Amazon DynamoDB Stream",
+  "description": "Sample Lambda ESM Filter rules for DynamoDB Stream triggers",
+  "language": "Node.js",
+  "level": "200",
+  "framework": "SAM",
+  "introBox": {
+    "headline": "How it works",
+    "text": [
+      "Use this code to test out different trigger filters for your Lambda functions. You can use event filtering to control which events Lambda sends to your function for processing. You can use this template to explore and test how to configure event filtering for Amazon DynamoDB Stream messages triggering a Lambda function.",
+      "Please note that this template is meant to be for testing, you can subscribe more than two Lambda functions to a DynamoDB Stream, but you'll likely experience read throttling, refer to the GitHub template README for more information.",
+      "The SAM template deploys multiple Lambda functions, a single stream-enabled Amazon DynamoDB Table and the permissions required to run the application. The template enforces 3 days retention period for all AWS Lambda CloudWatch logs. All AWS Lambda functions are deployed to NodeJS 18 runtime running on ARM64 processors powered by AWS Graviton."
+    ]
+  },
+  "gitHub": {
+    "template": {
+      "repoURL": "https://github.com/aws-samples/serverless-patterns/tree/main/lambda-esm-ddb-filters-sam/",
+      "templateURL": "serverless-patterns/lambda-esm-ddb-filters-sam",
+      "projectFolder": "lambda-esm-ddb-filters-sam",
+      "templateFile": "lambda-esm-ddb-filters-sam/template.yaml"
+    }
+  },
+  "resources": {
+    "headline": "Additional resources",
+    "bullets": [
+      {
+        "text": "Lambda event filtering",
+        "link": "https://docs.aws.amazon.com/lambda/latest/dg/invocation-eventfiltering.html"
+      }
+    ]
+  },
+  "deploy": {
+    "text": [
+      "sam build",
+      "sam deploy --guided"
+    ]
+  },
+  "testing": {
+    "headline": "Testing",
+    "text": [
+      "See the GitHub repo for detailed testing instructions."
+    ]
+  },
+  "cleanup": {
+    "headline": "Cleanup",
+    "text": [
+      "Delete the stack: <code>sam delete --stack-name STACK_NAME</code>."
+    ]
+  },
+  "authors": [
+    {
+      "name": "Dmitry Gulin",
+      "image": "https://s.gravatar.com/avatar/223055bd132d244f6a96c3aef7453a5a",
+      "bio": "Senior Modernization Architect, AWS",
+      "linkedin": "dmitry-gulin"
+    }
+  ]
+}
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