An example SAM template that creates a DynamoDB table, a Lambda function that writes to DynamoDB, and a CloudWatch Event trigger

template.yaml

AWSTemplateFormatVersion: '2010-09-09'
Transform: 'AWS::Serverless-2016-10-31'
Description: An app that includes a DynamoDB table, Lambda function that writes to DynamoDB, and CloudWatch Event trigger

Resources:
  LambdaWriteToDynamoDB:
    # A function that writes to a DynamoDB table on a schedule
    Type: 'AWS::Serverless::Function'
    Properties:
      FunctionName: LambdaWriteToDynamoDB
      Handler: LambdaWriteToDynamoDB.lambda_handler
      Runtime: python3.7
      CodeUri: ./LambdaWriteToDynamoDB
      Description: A function that writes to a DynamoDB table on a schedule
      MemorySize: 128
      Timeout: 120
      Policies:
      # Read more about SAM policy templates here
      # https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-policy-templates.html
       - AWSLambdaExecute
       - DynamoDBCrudPolicy:
          TableName: !Ref MyDynamoDBTable
      Environment:
        Variables:
          TABLE_NAME: !Ref MyDynamoDBTable
      Events:
        MyCloudWatchEvent:
          Type: Schedule
          Properties:
            # Read more about schedule expressions here: 
            # https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/ScheduledEvents.html
            # This event runs every Friday at 16 UTC/9AM PST
            Schedule: cron(0 16 ? * FRI *)
            
  MyDynamoDBTable:
    Type: AWS::DynamoDB::Table
    DeletionPolicy: Retain
    Properties:
      TableName: MyDynamoDBTable
      AttributeDefinitions:
        - AttributeName: ListId
          AttributeType: S
        - AttributeName: Date
          AttributeType: S
      KeySchema:
        - AttributeName: ListId
          KeyType: HASH
        - AttributeName: Date
          KeyType: RANGE
      BillingMode: PAY_PER_REQUEST
      ProvisionedThroughput:
        ReadCapacityUnits: 0
        WriteCapacityUnits: 0