Create POST API

In this step, we will add the POST method to our REST API so that the frontend can create new books via the book_create Lambda function.

Adding a new method requires re-creating the API deployment. Since BookApiDeployment cannot be updated in-place while a stage depends on it, we must do this in two phases:

• Phase 1: Comment out the deployment, deploy to detach the stage from it, letting CloudFormation delete the old deployment.
• Phase 2: Add the POST method, uncomment the deployment (now with both GET + POST as dependencies), and deploy again.

Phase 1 — Remove old Deployment

1. Open the template.yaml file in the fcaj-book-shop folder.

2. Comment out the BookApiDeployment block, and also comment the DeploymentId line inside BookApiStage, so CloudFormation can delete the old deployment cleanly:

   # BookApiDeployment:
   #   Type: AWS::ApiGateway::Deployment
   #   Properties:
   #     RestApiId: !Ref BookApi
   #   DependsOn:
   #     - BookApiGet
   
   BookApiStage:
     Type: AWS::ApiGateway::Stage
     Properties:
       RestApiId: !Ref BookApi
       StageName: !Ref stage
       # DeploymentId: !Ref BookApiDeployment
   

   

3. Run the following commands to validate, build, and deploy:

   sam validate
   sam build
   

   

   sam deploy
   

   The changeset shows:

   • Modify BookApiStage (AWS::ApiGateway::Stage)
   • Delete BookApiDeployment (AWS::ApiGateway::Deployment)

   Enter y to confirm.

   

4. Wait for the deployment to complete.

   

Phase 2 — Add POST Method and Redeploy

5. Add the BookApiCreate method and its invoke permission resource after BookApiGetInvokePermission:

   BookApiCreate:
     Type: AWS::ApiGateway::Method
     Properties:
       HttpMethod: POST
       RestApiId: !Ref BookApi
       ResourceId: !Ref BookApiResource
       AuthorizationType: NONE
       Integration:
         Type: AWS_PROXY
         IntegrationHttpMethod: POST # For Lambda integrations, you must set the integration method to POST
         Uri: !Sub >-
           arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${BookCreate.Arn}/invocations
         IntegrationResponses:
           - StatusCode: "200"
             ResponseParameters:
               method.response.header.Access-Control-Allow-Origin: "'*'"
               method.response.header.Access-Control-Allow-Methods: "'GET,POST,OPTIONS'"
               method.response.header.Access-Control-Allow-Headers: "'Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token'"
       MethodResponses:
         - StatusCode: "200"
           ResponseParameters:
             method.response.header.Access-Control-Allow-Origin: "'*'"
             method.response.header.Access-Control-Allow-Methods: "'GET,POST,OPTIONS'"
             method.response.header.Access-Control-Allow-Headers: "'Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token'"
   
   BookApiCreateInvokePermission:
     Type: AWS::Lambda::Permission
     Properties:
       FunctionName: !Ref BookCreate
       Action: lambda:InvokeFunction
       Principal: apigateway.amazonaws.com
       SourceAccount: !Ref "AWS::AccountId"
   

   

6. Now uncomment the BookApiDeployment block and the DeploymentId inside BookApiStage. Update DependsOn to include both BookApiGet and BookApiCreate:

   BookApiDeployment:
     Type: AWS::ApiGateway::Deployment
     Properties:
       RestApiId: !Ref BookApi
     DependsOn:
       - BookApiGet
       - BookApiCreate
   
   BookApiStage:
     Type: AWS::ApiGateway::Stage
     Properties:
       RestApiId: !Ref BookApi
       StageName: !Ref stage
       DeploymentId: !Ref BookApiDeployment
   

   

7. Run the following commands again to build and deploy:

   sam validate
   sam build
   

   

   sam deploy
   

   The changeset shows new resources being added:

   • Add BookApiCreate (AWS::ApiGateway::Method)
   • Add BookApiDeployment (AWS::ApiGateway::Deployment)
   • Add BookApiCreateInvokePermission (AWS::Lambda::Permission)
   • Modify BookApiStage (AWS::ApiGateway::Stage)

   Enter y to confirm.

   

8. Wait for the deployment to complete. You should see Successfully created/updated stack - fcaj-book-shop in ap-southeast-1.

   

Verify on AWS Console

9. Open the AWS API Gateway console. Click on the fcaj-serverless-api REST API.

   

10. At the fcaj-serverless-api page:

    • Click Resources in the left menu.
    • Select POST under the /books resource.
    • Click the Lambda integration tooltip — confirm the integrated function is book_create.

    

11. Click Stages in the left menu.

    • Expand staging → /books → select POST.
    • Copy and save the Invoke URL — this is the same base URL as the GET endpoint, since both methods share the same /books resource path.

    Example: https://1bupjnr42d.execute-api.ap-southeast-1.amazonaws.com/staging/books