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Why use API Gateway as a proxy for AWS APIs?
Many AWS services provide APIs that applications depend on directly for their functionality. Examples include:
- Amazon DynamoDB – An API-accessible NoSQL database.
- Amazon Kinesis – Real-time ingestion of streaming data via API.
- Amazon CloudWatch – API-driven metrics collection and retrieval.
If AWS already exposes internet-accessible APIs, why would you want to use API Gateway as a proxy for them? Why not allow applications to just directly depend on the AWS service API itself?
Using Amazon API Gateway as a proxy for DynamoDB in AWS CDK
In this article, I will show you how to implement Amazon API Gateway as a proxy for DynamoDB by using AWS cdk. It is simpler than you think.
In this article we're going to create an Http API with 2 routes:
- GET /posts/{id} get a post by ID
- POST /posts create a post
CDK snippets
Creating the DynamoDB Table
const postTable = new dynamodb.Table(this, 'PostTable', {
partitionKey: {
name: 'id',
type: dynamodb.AttributeType.STRING,
},
removalPolicy: RemovalPolicy.DESTROY,
billingMode: dynamodb.BillingMode.PAY_PER_REQUEST,
})
Creating the APIs
const api = new apigateway.RestApi(this, 'api-gateway-dynamodb', {
description: 'Demo API Gateway with DynamoDB',
// This will automatically set up OPTIONS responses for all your endpoints.
defaultCorsPreflightOptions: {
// allow all origins,
allowOrigins: apigateway.Cors.ALL_ORIGINS,
},
})
Creating the Post API
const modelResource = api.root.addResource('posts')
// Create post
modelResource.addMethod(
'POST',
new apigateway.AwsIntegration({
service: 'dynamodb',
action: 'PutItem',
options: {
credentialsRole: role,
integrationResponses: [
{
statusCode: '200',
responseTemplates: {
'application/json': `
{
"status": "OK"
}`,
},
},
...errorResponses,
],
requestTemplates: {
'application/json': `
#set($inputRoot = $input.path('$'))
{
"TableName": "${postTable.tableName}",
"Item": {
"id": {
"S": "$inputRoot.id"
},
"title": {
"S": "$inputRoot.title"
},
"body": {
"S": "$inputRoot.body"
}
},
"ConditionExpression": "attribute_not_exists(id)"
}`,
},
},
}),
methodOptions
)
The code for this article is available on GitHub
Let's go over what we did in the code snippet.
- We create a proxy resource
- We added a route to our API. The route is for POST requests to /posts.
Let's deploy to test our API. We'll write the API url to a file on the local file system
npx aws-cdk deploy \
--outputs-file ./cdk-outputs.json
That all, now you can test your api
Clean up
Don't forget clean all resource avoid unexpected cost.
npx cdk destroy
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