Example of an AWS Lambda Destinations configuration for AWS Lambda functions within an application.

api.yaml

# You don't need this, but here it is anyways :)
openapi: "3.0.1"
info:
  title: "Translation API (Async)"
  version: "1.0.0"

paths:
  /:
    post:
      summary: Create new translation request
      responses:
        "200":
          headers:
            Access-Control-Allow-Origin:
              type: "string"
        "400":
          headers:
            Access-Control-Allow-Origin:
              type: "string"
      x-amazon-apigateway-integration:
        type: "aws"
        credentials:
          Fn::GetAtt: [ DDBCrudRole, Arn ]
        uri: { "Fn::Sub": "arn:aws:apigateway:${AWS::Region}:dynamodb:action/UpdateItem" }
        httpMethod: "POST"
        requestTemplates:
          application/json: { "Fn::Sub": "{\"TableName\": \"${TranslationsTable}\",\
            \"ConditionExpression\":\"attribute_not_exists(id)\",\
            \"Key\": {\"id\": {\"S\": \"$context.requestId\"}, \"type\": {\"S\": \"original\"}},\
            \"ExpressionAttributeNames\": {\"#ts\": \"timestamp\", \"#oi\": \"originalId\", \"#d\": \"data\", \"#c\": \"culture\"},\
            \"ExpressionAttributeValues\":{\
              \":ts\": {\"S\": \"$context.requestTimeEpoch\"},\
              \":oi\": {\"S\": \"original-$context.requestId\"},\
              \":d\": {\"S\": $input.json('$.data')},\
              \":c\": {\"L\": [#foreach($culture in $input.path('$.culture')){\"S\": \"$culture\"}#if($foreach.hasNext),#end#end]}
            }, \
            \"UpdateExpression\": \"SET #ts = :ts, #oi = :oi, #d = :d, #c = :c\",\
            \"ReturnValues\": \"ALL_NEW\"}" }
        passthroughBehavior: "when_no_templates"
        responses:
          "200":
            statusCode: "200"
            responseParameters:
              method.response.header.Access-Control-Allow-Origin: "'*'"
            responseTemplates:
              application/json: "{\"success\": true}"
          default:
            statusCode: "400"
            responseParameters:
              method.response.header.Access-Control-Allow-Origin: "'*'"
            responseTemplates:
              application/json: "{\"success\": false}"
    
    get:
      summary: Fetch all translations request
      responses:
        "200":
          description: "succesful response"
          headers:
            Access-Control-Allow-Origin:
              type: "string"
        "400":
          description: "unsuccesful response"
          headers:
            Access-Control-Allow-Origin:
              type: "string"
      x-amazon-apigateway-integration:
        type: "AWS"
        credentials:
          Fn::GetAtt: [ DDBReadRole, Arn ]
        uri: { "Fn::Sub": "arn:aws:apigateway:${AWS::Region}:dynamodb:action/Scan" }
        httpMethod: "POST"
        requestTemplates:
          application/json: { "Fn::Sub": "{\"TableName\": \"${TranslationsTable}\",\"IndexName\":\"Originals\"}" }
        passthroughBehavior: "when_no_templates"
        responses:
          "200":
            statusCode: "200"
            responseParameters:
              method.response.header.Access-Control-Allow-Origin: "'*'"
            responseTemplates:
              application/json: "#set($items = $input.path('$.Items')){\
                \"success\": true,\
                \"Items\": [#foreach($item in $items){\
                \"id\":\"$item.id.S\",\
                \"data\":\"$item.data.S\",\
                \"sentiment\": \"$item.sentiment.S\",\
                \"timestamp\": \"$item.timestamp.S\",\
                \"culture\": [#foreach($c in $item.culture.L)\"$c.S\"#if($foreach.hasNext), #end#end]\
                }#if($foreach.hasNext),#end#end]}"
          default:
            statusCode: "400"
            responseParameters:
              method.response.header.Access-Control-Allow-Origin: "'*'"
            responseTemplates:
              application/json: "{\"success\": false}"
  /{id}:
    get:
      summary: Fetch all translations request
      parameters:
        - in: path
          name: id
          schema:
            type: string
          required: true
          description: Tranlation id
      responses:
        "200":
          description: "succesful response"
          headers:
            Access-Control-Allow-Origin:
              type: "string"
        "400":
          description: "unsuccesful response"
          headers:
            Access-Control-Allow-Origin:
              type: "string"
      x-amazon-apigateway-integration:
        type: "AWS"
        credentials:
          Fn::GetAtt: [ DDBReadRole, Arn ]
        uri: { "Fn::Sub": "arn:aws:apigateway:${AWS::Region}:dynamodb:action/Query" }
        httpMethod: "POST"
        requestTemplates:
          application/json: { "Fn::Sub": "{\
              \"TableName\": \"${TranslationsTable}\",\
              \"KeyConditionExpression\": \"id = :hkey\",\
              \"ExpressionAttributeValues\": {\":hkey\": {\"S\": \"$input.params().path.id\"}}}"
            }
        passthroughBehavior: "when_no_templates"
        responses:
          "200":
            statusCode: "200"
            responseParameters:
              method.response.header.Access-Control-Allow-Origin: "'*'"
            responseTemplates:
              application/json: "#set($items = $input.path('$.Items')){\
                \"success\": true,\
                \"Items\": [#foreach($item in $items){\
                \"id\":\"$item.id.S\",\
                \"data\":\"$item.data.S\",\
                \"timestamp\": \"$item.timestamp.N\",\
                \"type\": \"$item.type.S\",\
                #if($item.originalId.S.toString() != \"\")\
                \"sentiment\": \"$item.sentiment.S\",\
                \"originalId\": \"$item.originalId.S\",\
                \"culture\": [#foreach($c in $item.culture.L)\"$c.S\"#if($foreach.hasNext), #end#end]\
                #else\"culture\": \"$item.culture.S\"#end\
                }#if($foreach.hasNext),#end#end]}"
          default:
            statusCode: "400"
            responseParameters:
              method.response.header.Access-Control-Allow-Origin: "'*'"
            responseTemplates:
              application/json: "{\"success\": false}"

template.yaml

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: Asynchronous Serverless Translation Application
Globals:
  Function:
    Timeout: 10
    Handler: app.lambdaHandler
    Runtime: nodejs12.x
    Layers:
      - arn:aws:lambda:us-west-2:700336187521:layer:aws-sdk:9
  Api:
    Cors:
      AllowOrigin: "'*'"
      AllowHeaders: "'*'"

Resources:
  SiteAPI:
    Type: AWS::Serverless::Api
    Properties:
      StageName: Prod
      EndpointConfiguration: REGIONAL
      TracingEnabled: true
      DefinitionBody:
        'Fn::Transform':
          Name: 'AWS::Include'
          Parameters:
            Location: './api.yaml'

  AudioBucket:
    Type: AWS::S3::Bucket

  ErrorDestination:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: error/
      Policies:
        - DynamoDBCrudPolicy: {TableName: !Ref TranslationsTable}
      Environment:
        Variables:
          TRANSLATIONS_TABLE: !Ref TranslationsTable
  
  StreamFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: stream/
      Policies:
        - Version: '2012-10-17'
          Statement:
            - Effect: Allow
              Action:
                - 'events:PutEvents'
              Resource: '*'
      Events:
        DDBStream:
          Type: DynamoDB
          Properties:
            Stream: !GetAtt TranslationsTable.StreamArn
            StartingPosition: LATEST ##TRIM_HORIZON
            BatchSize: 10
            Enabled: true

  TranslateFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: translate/
      Policies:
        - DynamoDBCrudPolicy: {TableName: !Ref TranslationsTable}
        - Version: '2012-10-17'
          Statement:
            - Effect: Allow
              Action:
                - 'translate:TranslateText'
                - 'comprehend:DetectDominantLanguage'
              Resource: '*'
      Events:
        TranslateEvent:
          Type: CloudWatchEvent
          Properties:
            Pattern: 
              source: 
                - "DBStream"
              detail-type: 
                - "translation"
      Environment:
        Variables:
          TRANSLATIONS_TABLE: !Ref TranslationsTable
      EventInvokeConfig:
        DestinationConfig:
          OnFailure:
            Type: Lambda
            Destination: !GetAtt ErrorDestination.Arn
  
  AudioFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: audio/
      Policies:
        - S3CrudPolicy: {BucketName: !Ref AudioBucket}
        - Version: '2012-10-17'
          Statement:
            - Effect: Allow
              Action:
                - 'polly:SynthesizeSpeech'
                - 'polly:StartSpeechSynthesisTask'
              Resource: '*'
      Events:
        AudioEvent:
          Type: CloudWatchEvent
          Properties:
            Pattern: 
              source: 
                - "DBStream"
              detail-type: 
                - "audio"
      Environment:
        Variables:
          AUDIO_BUCKET: !Ref AudioBucket
  
  FinalFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: final/
      Policies:
        - DynamoDBCrudPolicy: {TableName: !Ref TranslationsTable}
        - Version: '2012-10-17'
          Statement:
            - Effect: Allow
              Action:
                - 's3:PutObjectACL'
              Resource: '*'
      Events:
        AudioComplete:
          Type: S3
          Properties:
            Bucket: !Ref AudioBucket
            Events: s3:ObjectCreated:*
      Environment:
        Variables:
          TRANSLATIONS_TABLE: !Ref TranslationsTable

  SentimentFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: sentiment/
      Policies:
        - DynamoDBCrudPolicy: {TableName: !Ref TranslationsTable}
        - Version: '2012-10-17'
          Statement:
            - Effect: Allow
              Action:
                - 'comprehend:DetectSentiment'
              Resource: '*'
      Events:
        SentimentEvent:
          Type: CloudWatchEvent
          Properties:
            Pattern: 
              source: 
                - "DBStream"
              detail-type: 
                - "translation"
      Environment:
        Variables:
          TRANSLATIONS_TABLE: !Ref TranslationsTable

  TranslationsTable:
    Type: AWS::DynamoDB::Table
    Properties:
      BillingMode: PAY_PER_REQUEST
      KeySchema:
        - AttributeName: id
          KeyType: HASH
        - AttributeName: type
          KeyType: RANGE
      AttributeDefinitions:
        - AttributeName: id
          AttributeType: S
        - AttributeName: type
          AttributeType: S
        - AttributeName: originalId
          AttributeType: S
      StreamSpecification:
        StreamViewType: NEW_AND_OLD_IMAGES
      GlobalSecondaryIndexes:
        - IndexName: Originals
          KeySchema:
            - AttributeName: originalId
              KeyType: HASH
          Projection:
            NonKeyAttributes:
              - data
              - culture
              - timestamp
              - sentiment
            ProjectionType: INCLUDE

  ##   Dynamo DB Read Role
  DDBReadRole:
    Type: "AWS::IAM::Role"
    Properties:
      AssumeRolePolicyDocument:
        Version: "2012-10-17"
        Statement:
          -
            Effect: "Allow"
            Principal:
              Service: "apigateway.amazonaws.com"
            Action: 
              - "sts:AssumeRole"
      Policies:
        - PolicyName: DDBReadPolicy
          PolicyDocument:
            Version: '2012-10-17'
            Statement:
              Action:
              - dynamodb:GetItem
              - dynamodb:Scan
              - dynamodb:Query
              Effect: Allow
              Resource:
                - !GetAtt TranslationsTable.Arn

  ##   Dynamo DB Read/Write Role
  DDBCrudRole:
    Type: "AWS::IAM::Role"
    Properties:
      AssumeRolePolicyDocument:
        Version: "2012-10-17"
        Statement:
          -
            Effect: Allow
            Principal:
              Service: "apigateway.amazonaws.com"
            Action: 
              - "sts:AssumeRole"
      Policies:
        - PolicyName: DDBCrudPolicy
          PolicyDocument:
            Version: '2012-10-17'
            Statement:
              Action:
              - dynamodb:DeleteItem
              - dynamodb:UpdateItem
              Effect: Allow
              Resource: !GetAtt TranslationsTable.Arn