This project is a serverless application based on AWS CDK.
A user of this web application can use the interface to create, delete and complete task items.
First, start the frontend application from the frontend folder.
npm install # if not already done so
npm startThen, login with Auth0 to provide your identity.
Create a user with an email and a password or login with Google account.
A user can create a new task by clikcing the Add Task button.
A list of tasks is maintained for each credential so if you login with a different credential, you will have another task list.
You can logout by using the Login menu item.
Click the Add Task button to create a new task.
Simply fill in the task details, and press the Add button.
The new task will be stored in AWS DynamoDB table and reflected in the web application.
You can add as many tasks as you need.
You can mark the task completion by clicking the checkbox on the left.
Click the pencil button for the task item to edit it.
Update the task details and press the Update button.
Upload an image for a task by pressing the upload button (the middle red button next to the pencil button).
Choose an image file and press the Upload button.
The image will be uploaded to the user specific AWS S3 bucket securely using a pre-signed url.
You can delete a task by clicking the X button and confirm the deletion.
For the frontend, I used React + Redux (with Thunk) to keep track of the application states.
The backend uses the following AWS resources:
- An API Gateway
- Lambda functions
- S3 buckets
- A DynamoDB table
The API Gateway uses a Lambda authorizor to authorize users to access AWS resources via Lambda functions.
Before a request reaches to a Lambda function, there is a request validator checking the request body so it will not waste Lambda compute time if the request is not properly formed.
Each Lambda function is implemented in a separate file under the backend/src/lambda folder.
Lambda functions delegates the business logic to the code implemented in backend/src/businessLogic.ts.
The business logic uses other codes (in seperate files) to perform database CRUD operations and S3 handling.
All those codes make use of async/await or Promise features for better performance and readability.
A DynamoDB table is used to persist task items.
The userId is the partition key and the taskId is the sort key (items are fetched using the query method).
I decided to use AWS CDK (Cloud Development Kit) instead of the Serverless Framework so that I can take advantage of local deployment feature and easier debugging.
On top of this, I understand better how the AWS resource allocation and permission grant works.
The best part of CDK is that it compiles and I can easily find bugs.
Also, associating IAM roles and permissions to each function is pretty straight forward.
AWS X-Ray is enabled so that it is easy to find out where an error has occurred.
AWS CloudWatch Log is another way to troubleshoot the backend logic.
