template.yaml

AWSTemplateFormatVersion: '2010-09-09'
Description: Add a TTL to records being inserted into a DynamoDB table
Transform: AWS::Serverless-2016-10-31

Parameters:
  ttlReferenceAttribute:
    Type: String
    Default: ''
    Description: Base the TTL on this attribute
  timeToLive:
    Type: String
    Default: ''
    Description: Add this many days to the ttlReferenceAttribute and use it as the ttl value
  ttlAttributeName:
    Type: String
    Default: ttl
    Description: Name of the attribute to create as the ttl
  tableName:
    Type: String
    Default: ''
    Description: DynamoDB Table to apply the ttl to
  streamARN:
    Type: String
    Description: The ARN of the DynamoDB stream

Resources:
  TTLFunction:
    Type: AWS::Serverless::Function
    Properties:
      FunctionName: !Sub "DynamoDBAddTTL-${tableName}"
      Description: !Sub "Add a TTL to records being inserted into ${tableName}"
      Runtime: python3.13
      CodeUri: src/
      Handler: dynamodb-add-ttl.lambda_handler
      MemorySize: 128
      Timeout: 20
      Environment:
        Variables:
          ttl_reference_attribute: !Ref 'ttlReferenceAttribute'
          time_to_live_days: !Ref 'timeToLive'
          ttl_attribute_name: !Ref 'ttlAttributeName'
      Events:
        DynamoDB:
          Type: DynamoDB
          Properties:
            BatchSize: 1
            StartingPosition: LATEST
            Stream: !Ref streamARN
      Policies:
        - Version: 2012-10-17
          Statement:
            - Sid: SourceStream
              Action:
                - dynamodb:GetRecords
                - dynamodb:GetShardIterator
                - dynamodb:DescribeStream
                - dynamodb:ListStreams
              Effect: Allow
              Resource: arn:aws:dynamodb:*:*:table/*/stream/*
            - Sid: DynamoDB
              Effect: Allow
              Action:
                - dynamodb:UpdateItem
              Resource: !Sub "arn:aws:dynamodb:${AWS::Region}:*:table/${tableName}"