Amazon API Gateway → Step Functions→ DynamoDBという構成で、データの新規登録や取得処理を試してみた

$ aws dynamodb create-table \
    --table-name RestaurantReservations \
    --attribute-definitions \
        AttributeName=PhoneNumber,AttributeType=S \
        AttributeName=ReservationTime,AttributeType=S \
    --key-schema \
        AttributeName=PhoneNumber,KeyType=HASH \
        AttributeName=ReservationTime,KeyType=RANGE \
    --billing-mode PAY_PER_REQUEST

{
  "Comment": "レストラン予約フロー",
  "QueryLanguage": "JSONata",
  "StartAt": "RouteRequest",
  "States": {
    "RouteRequest": {
      "Type": "Choice",
      "Choices": [
        {
          "Condition": "{% $states.input.action = 'create' %}",
          "Next": "CreateReservation"
        },
        {
          "Condition": "{% $states.input.action = 'check' %}",
          "Next": "CheckReservation"
        }
      ],
      "Default": "InvalidAction"
    },
    "CreateReservation": {
      "Type": "Task",
      "Resource": "arn:aws:states:::aws-sdk:dynamodb:putItem",
      "Arguments": {
        "TableName": "RestaurantReservations",
        "Item": {
          "PhoneNumber": {
            "S": "{% $states.input.phone %}"
          },
          "ReservationTime": {
            "S": "{% $states.input.time %}"
          },
          "CustomerName": {
            "S": "{% $states.input.name %}"
          },
          "PeopleCount": {
            "N": "{% $string($states.input.count) %}"
          },
          "Status": {
            "S": "RESERVED"
          }
        },
        "ConditionExpression": "attribute_not_exists(PhoneNumber)"
      },
      "Output": {
        "status": "success",
        "message": "ご予約を承りました。"
      },
      "Catch": [
        {
          "ErrorEquals": [
            "DynamoDB.ConditionalCheckFailedException"
          ],
          "Next": "AlreadyExists"
        }
      ],
      "End": true
    },
    "CheckReservation": {
      "Type": "Task",
      "Resource": "arn:aws:states:::aws-sdk:dynamodb:query",
      "Arguments": {
        "TableName": "RestaurantReservations",
        "KeyConditionExpression": "PhoneNumber = :p AND ReservationTime >= :now",
        "ExpressionAttributeValues": {
          ":p": {
            "S": "{% $states.input.phone %}"
          },
          ":now": {
            "S": "{% $now() %}"
          }
        }
      },
      "Output": {
        "status": "success",
        "found": "{% $count($states.result.Items) > 0 %}",
        "reservations": "{% $states.result.Items.{ 'name': CustomerName.S, 'time': ReservationTime.S, 'count': PeopleCount.N, 'status': Status.S } %}",
        "message": "{% $count($states.result.Items) > 0 ? 'これからのご予約が見つかりました。' : '現在、これからのご予約は承っておりません。' %}"
      },
      "End": true
    },
    "AlreadyExists": {
      "Type": "Pass",
      "Output": {
        "status": "error",
        "message": "お客様は既に同じ日時でご予約されています。重複予約はできません。"
      },
      "End": true
    },
    "InvalidAction": {
      "Type": "Pass",
      "Output": {
        "status": "error",
        "message": "不正な操作です。"
      },
      "End": true
    }
  }
}

# 信頼ポリシー作成
echo '{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Service": "apigateway.amazonaws.com"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}' > trust-policy.json

# ロール作成
aws iam create-role \
    --role-name APIGatewayToStepFunctionsRole \
    --assume-role-policy-document file://trust-policy.json

# 権限付与
aws iam attach-role-policy \
    --role-name APIGatewayToStepFunctionsRole \
    --policy-arn arn:aws:iam::aws:policy/AWSStepFunctionsFullAccess

# ARNの確認 (★これを控える)
aws iam get-role \
    --role-name APIGatewayToStepFunctionsRole \
    --query 'Role.Arn' \
    --output text

#set($phone = $input.params('phone'))
{
  "stateMachineArn": "arn:aws:states:ap-northeast-1:YOUR_ACCOUNT_ID:stateMachine:RestaurantReservationFlow",
  "input": "{\"action\": \"check\", \"phone\": \"$util.escapeJavaScript($phone)\"}"
}

{
  "stateMachineArn": "arn:aws:states:ap-northeast-1:YOUR_ACCOUNT_ID:stateMachine:RestaurantReservationFlow",
  "input": "$util.escapeJavaScript($input.json('$').replaceFirst('^\s*\{', '{ \"action\": \"create\", '))"
}

#set($result = $input.path('$'))

#if($result.status == 'SUCCEEDED')
  ## 成功時は output の中身（JSON文字列）をそのまま展開してレスポンス本文にする
  $result.output
#else
  ## 失敗時は500エラーとし、エラー内容を返す
  #set($context.responseOverride.status = 500)
  {
    "error": "$result.error",
    "cause": "$result.cause"
  }
#end

curl -X POST "https://{api-id}.execute-api.ap-northeast-1.amazonaws.com/dev/reservations" \
     -H "Content-Type: application/json" \
     -d '{
           "phone": "09011111111",
           "time": "2026-01-14T12:00",
           "name": "適当な名前",
           "count": 2
         }'

{
  "status": "success",
  "message": "ご予約を承りました。"
}

{"billingDetails":{"billedDurationInMilliseconds":100,"billedMemoryUsedInMB":64},"executionArn":"arn:aws:states:ap-northeast-1:111111111111:express:RestaurantReservationFlow:4542c1e7-a5ce-46ba-80c4-78ca35d7730b:3168f3c7-436e-4154-8d76-3b39a3f0bc05","input":"{ \"action\": \"create\", \"phone\":\"09011111111\",\"time\":\"2026-01-14T12:00\",\"name\":\"適当な名前\",\"count\":2}","inputDetails":{"__type":"com.amazonaws.swf.base.model#CloudWatchEventsExecutionDataDetails","included":true},"name":"4542c1e7-a5ce-46ba-80c4-78ca35d7730b","output":"{\"status\":\"success\",\"message\":\"ご予約を承りました。\"}","outputDetails":{"__type":"com.amazonaws.swf.base.model#CloudWatchEventsExecutionDataDetails","included":true},"startDate":1.768268689381E9,"stateMachineArn":"arn:aws:states:ap-northeast-1:111111111111:stateMachine:RestaurantReservationFlow","status":"SUCCEEDED","stopDate":1.768268689451E9,"traceHeader":"Root=1-6965a391-ec956495d41a159d021c0498;Sampled=1"}

curl "https://{api-id}.execute-api.ap-northeast-1.amazonaws.com/dev/reservations?phone=09011111111"

{
  "status": "success",
  "found": true,
  "reservations": [
    {
      "name": "佐藤 次郎",
      "time": "2026-01-14T12:00",
      "count": "2",
      "status": "RESERVED"
    }
    ,
    {
      "name": "佐藤 次郎",
      "time": "2026-01-16T12:00",
      "count": "3",
      "status": "RESERVED"
    }
  ],
  "message": "これからのご予約が見つかりました。"
}