How to create a CRUD API with serverless using DynamoDB

In this example we will look at how to create a CRUD API with serverless using DynamoDB. We’ll be using Serverless Stack (SST). Our API will be creating, reading, updating, and deleting notes.

Requirements

• Node.js >= 10.15.1
• We’ll be using TypeScript
• An AWS account with the AWS CLI configured locally

Create an SST app

Let’s start by creating an SST app.

$ npm init sst -- typescript-starter crud-api-dynamodb
$ cd crud-api-dynamodb

By default our app will be deployed to an environment (or stage) called dev and the us-east-1 AWS region. This can be changed in the sst.json in your project root.

{
  "name": "crud-api-dynamodb",
  "region": "us-east-1",
  "main": "stacks/index.ts"
}

Project layout

An SST app is made up of two parts.

1. stacks/ — App Infrastructure

   The code that describes the infrastructure of your serverless app is placed in the stacks/ directory of your project. SST uses AWS CDK, to create the infrastructure.

2. backend/ — App Code

   The code that’s run when your API is invoked is placed in the backend/ directory of your project.

Adding DynamoDB

Amazon DynamoDB is a reliable and highly-performant NoSQL database that can be configured as a true serverless database. Meaning that it’ll scale up and down automatically. And you won’t get charged if you are not using it.

Replace the stacks/MyStack.ts with the following.

import { Api, StackContext, Table } from "@serverless-stack/resources";

export function MyStack({ stack }: StackContext) {
  // Create the table
  const table = new Table(stack, "Notes", {
    fields: {
      userId: "string",
      noteId: "string",
    },
    primaryIndex: { partitionKey: "userId", sortKey: "noteId" },
  });
}

This creates a serverless DynamoDB table using Table. Our table is going to look something like this:

Setting up our routes

Now let’s add the API.

Add this after the Table definition in stacks/MyStack.ts.

// Create the HTTP API
const api = new Api(stack, "Api", {
  defaults: {
    function: {
      // Pass in the table name to our API
      environment: {
        tableName: table.tableName,
      },
    },
  },
  routes: {
    "GET /notes": "functions/list.handler",
    "POST /notes": "functions/create.handler",
    "GET /notes/{id}": "functions/get.handler",
    "PUT /notes/{id}": "functions/update.handler",
    "DELETE /notes/{id}": "functions/delete.handler",
  },
});

// Allow the API to access the table
api.attachPermissions([table]);

// Show the API endpoint in the output
stack.addOutputs({
  ApiEndpoint: api.url,
});

We are creating an API here using the Api construct. And we are adding five routes to it.

GET /notes
POST /notes
GET /notes/{id}
PUT /notes/{id}
DELETE /notes/{id}

These will be getting a list of notes, creating a note, getting, updating, and deleting a specific note respectively.

We also pass in the name of our DynamoDB table to our API as an environment variable called tableName. And we allow our API to access (read and write) the table instance we just created.

Create a note

Let’s turn towards the functions that’ll be powering our API. Starting with the one that creates our note.

Add the following to backend/functions/create.ts.

import { DynamoDB } from "aws-sdk";
import * as uuid from "uuid";
import { APIGatewayProxyHandlerV2 } from "aws-lambda";

const dynamoDb = new DynamoDB.DocumentClient();

export const handler: APIGatewayProxyHandlerV2 = async (event) => {
  const data = JSON.parse(event.body);

  const params = {
    // Get the table name from the environment variable
    TableName: process.env.tableName,
    Item: {
      userId: "123",
      noteId: uuid.v1(), // A unique uuid
      content: data.content, // Parsed from request body
      createdAt: Date.now(),
    },
  };
  await dynamoDb.put(params).promise();

  return {
    statusCode: 200,
    body: JSON.stringify(params.Item),
  };
};

Here we are creating a new row in our DynamoDB table. First we JSON parse the request body. That gives us the content of the note. Then we are hard coding the userId to 123 for now. Our API will not be tied to a user. We’ll tackle that in a later example. We are also using a uuid package to generate a unique noteId.

Let’s install both the packages we are using here.

Run the below command in the backend/ folder.

$ npm install aws-sdk uuid

Read the list of notes

Next, let’s write the function that’ll fetch all our notes.

Add the following to backend/functions/list.ts.

import { DynamoDB } from "aws-sdk";

const dynamoDb = new DynamoDB.DocumentClient();

export async function handler() {
  const params = {
    // Get the table name from the environment variable
    TableName: process.env.tableName,
    // Get all the rows where the userId is our hardcoded user id
    KeyConditionExpression: "userId = :userId",
    ExpressionAttributeValues: {
      ":userId": "123",
    },
  };
  const results = await dynamoDb.query(params).promise();

  return {
    statusCode: 200,
    body: JSON.stringify(results.Items),
  };
}

Here we are getting all the notes for our hard coded userId, 123.

Read a specific note

We’ll do something similar for the function that gets a single note.

Create a backend/functions/get.ts.

import { DynamoDB } from "aws-sdk";
import { APIGatewayProxyHandlerV2 } from "aws-lambda";

const dynamoDb = new DynamoDB.DocumentClient();

export const handler: APIGatewayProxyHandlerV2 = async (event) => {
  const params = {
    // Get the table name from the environment variable
    TableName: process.env.tableName,
    // Get the row where the noteId is the one in the path
    Key: {
      userId: "123",
      noteId: event.pathParameters.id,
    },
  };
  const results = await dynamoDb.get(params).promise();

  return {
    statusCode: 200,
    body: JSON.stringify(results.Item),
  };
};

We are getting the note with the id that’s passed in through the API endpoint path. The event.pathParameters.id corresponds to the id in /notes/{id}.

Update a note

Now let’s update our notes.

Add a backend/functions/update.ts with:

import { DynamoDB } from "aws-sdk";
import { APIGatewayProxyHandlerV2 } from "aws-lambda";

const dynamoDb = new DynamoDB.DocumentClient();

export const handler: APIGatewayProxyHandlerV2 = async (event) => {
  const data = JSON.parse(event.body);

  const params = {
    // Get the table name from the environment variable
    TableName: process.env.tableName,
    // Get the row where the noteId is the one in the path
    Key: {
      userId: "123",
      noteId: event.pathParameters.id,
    },
    // Update the "content" column with the one passed in
    UpdateExpression: "SET content = :content",
    ExpressionAttributeValues: {
      ":content": data.content || null,
    },
    ReturnValues: "ALL_NEW",
  };

  const results = await dynamoDb.update(params).promise();

  return {
    statusCode: 200,
    body: JSON.stringify(results.Attributes),
  };
};

We are first JSON parsing the request body. We use the content we get from it, to update the note. The ALL_NEW property means that this update call will return the updated row.

Delete a note

To complete the CRUD operations, let’s delete the note.

Add this to backend/delete.ts.

import { DynamoDB } from "aws-sdk";
import { APIGatewayProxyHandlerV2 } from "aws-lambda";

const dynamoDb = new DynamoDB.DocumentClient();

export const handler: APIGatewayProxyHandlerV2 = async (event) => {
  const params = {
    // Get the table name from the environment variable
    TableName: process.env.tableName,
    // Get the row where the noteId is the one in the path
    Key: {
      userId: "123",
      noteId: event.pathParameters.id,
    },
  };
  await dynamoDb.delete(params).promise();

  return {
    statusCode: 200,
    body: JSON.stringify({ status: true }),
  };
};

Now let’s test what we’ve created so far.

Starting your dev environment

SST features a Live Lambda Development environment that allows you to work on your serverless apps live.

$ npm start

The first time you run this command it’ll take a couple of minutes to deploy your app and a debug stack to power the Live Lambda Development environment.

===============
 Deploying app
===============

Preparing your SST app
Transpiling source
Linting source
Deploying stacks
dev-rest-api-dynamodb-my-stack: deploying...

 ✅  dev-rest-api-dynamodb-my-stack


Stack dev-rest-api-dynamodb-my-stack
  Status: deployed
  Outputs:
    ApiEndpoint: https://t34witddz7.execute-api.us-east-1.amazoncom

The ApiEndpoint is the API we just created.

Let’s test our endpoint using the integrated SST Console. The SST Console is a web based dashboard to manage your SST apps Learn more about it in our docs.

Let’s create our first note, go to the API explorer and click on the POST /notes route.

Note, The API explorer lets you make HTTP requests to any of the routes in your Api construct. Set the headers, query params, request body, and view the function logs with the response.

In the Headers tab enter Content-type in Header 1 input and application/json in Value 1 input. Go to the Body tab and paste the below json.

{ "content": "Hello World" }

Now, hit the Send button to send the request.

This should create a new note.

To retrieve the created note, go to GET /notes/{id} route and in the URL tab enter the id of the note we created in the id field and click the Send button to get that note.

Also let’s go to the DynamoDB tab in the SST Console and check that the value has been created in the table.

Note, The DynamoDB explorer allows you to query the DynamoDB tables in the Table constructs in your app. You can scan the table, query specific keys, create and edit items.

Now to update our note, we need to make a PUT request, go to PUT /notes/{id} route.

In the URL tab, enter the id of the note we created and in the body tab and enter the below json value and hit Send.

{ "content": "Updating the note" }

This should respond with the updated note.

Click the Send button of the GET /notes route to get a list of notes.

You should see the list of notes.

To delete a note, go to the DELETE /notes/{id} and enter the id of the note to delete in the URL tab and hot Send.

Making changes

Let’s make a quick change to test our Live Lambda Development environment. We want our get function to return an error if it cannot find the note.

Replace the return statement in backend/gets.ts with:

return results.Item
  ? {
      statusCode: 200,
      body: JSON.stringify(results.Item),
    }
  : {
      statusCode: 404,
      body: JSON.stringify({ error: true }),
    };

Now let’s send an invalid request by entering a random note id which is not present in the table.

You should see an error being printed out.

Deploying to prod

To wrap things up we’ll deploy our app to prod.

$ npm run deploy -- --stage prod

This allows us to separate our environments, so when we are working in dev, it doesn’t break the app for our users.

Once deployed, you should see something like this.

 ✅  prod-rest-api-dynamodb-my-stack


Stack prod-rest-api-dynamodb-my-stack
  Status: deployed
  Outputs:
    ApiEndpoint: https://ck198mfop1.execute-api.us-east-1.amazoncom

Run the below command to open the SST Console in prod stage to test the production endpoint.

npm run console -- --stage prod

Go to the API explorer and click Send button of the GET /notes route, to send a GET request.

Cleaning up

Finally, you can remove the resources created in this example using the following commands.

$ npm run remove
$ npm run remove -- --stage prod

Conclusion

And that’s it! We’ve got a completely serverless CRUD API. In another example, we’ll add authentication to our API, so we can fetch the notes for a given user. Check out the repo below for the code we used in this example. And leave a comment if you have any questions!