This document describes an AWS serverless architecture for a cart microservice using AWS Lambda, API Gateway, and DynamoDB. It includes components like API Gateway for the REST API frontend, Lambda functions to run the application code, and DynamoDB for the database. It provides instructions on setting up the resources, mapping the API to Lambda, and deploying the API for testing. The goal is to build a serverless REST API for basic cart operations like read, create, delete that avoids managing servers and scales automatically.

1. AWS Lambda- ServerLess
Arch
Cart Micro Service
API Gateway
Lambda
DynamoDB
Dhanu Gupta
January, 2016

2. AWS Lambda - Benefits

3. AWS Lambda – Working Model

4. Route 53
API Gateway
/cart
/read
/create
/delete
Lambda
/CartRequestRouter
/update
DynamoDB
cart
AWS Lambda - Cart Micro Service Arch
ASK
Mobile
Client
Users

5. Components
• AWS API Gateway
API Gateway helps developers deliver robust, secure, and scalable mobile
and web application back ends.
• AWS Lambda Functions
Run code without thinking about servers. Pay for only the compute time
you consume.
• DynamoDB
Amazon DynamoDB is a fast and flexible NoSQL database service for all
applications that need consistent, single-digit millisecond latency at any
scale. It is a fully managed cloud database and supports both document
and key-value store models.
• Deployment
JAVA, Gradle, Jenkins Deployment

6. AWS DynamoDB
• Create Table on DynamoDB
Name : ‘cart’
Partition Key : ‘loginId’ (String)
Sort key : ‘sku’ (String)
Read Capacity Units : 100
Write Capacity Units : 50
# Note: If you want to read more on provisioned read/write
capacities
http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ProvisionedThroughputIntro.html

7. AWS Lambda
• Create a new Lambda function
Name : `CartRequestRouter`
Handler : `com.org.cart.router.RequestRouter::lambdaHandler`
Runtime Env : `Java`
Memory : `1024`
Timeout : `30secs` to start with
Note :
1. Ensure your Lambda function is using the correct IAM role. The role must have
the ability to write/read to DynamoDB.
2. All Lambda interactions are logged in Cloudwatch logs. View the logs for
debugging.
• The Lambda function
`com.aol.cart.router.RequestRouter` -
` lambdaHandler(InputStream request, OutputStream response, Context context) `
• Review & create function.

8. AWS API Gateway
• Create a new API. Give it a name and description. This will
be our RESTful endpoint.
• Create a resource. The path should be ‘/cart’ , for
example.
• We need to add one more resource as ‘/read’ under cart
as’ /cart/read’. Create a GET method with Lambda
integration.
• Now let's setup the Integration Request. Cart Micro Service
GET request will be of type application/json. This
Integration step will map this type to a JSON object, which
Lambda requires. In the Integration Requests page create a
mapping template. Content-type is application/json and
template:

9. Mapping Template
{
"body" : $input.json('$'),
"headers": {
#foreach($header in $input.params().header.keySet())
"$header": "$util.escapeJavaScript($input.params().header.get($header))" #if($foreach.hasNext),#end #end
},
"params": {
#foreach($param in $input.params().path.keySet())
"$param": "$util.escapeJavaScript($util.urlDecode($input.params().path.get($param)))" #if($foreach.hasNext),#end
#end
},
"query": {
#foreach($queryParam in $input.params().querystring.keySet())
"$queryParam": "$util.escapeJavaScript($util.urlDecode($input.params().querystring.get($queryParam)))"
#if($foreach.hasNext),#end #end
},
"stage" : "$context.stage",
"requestId" : "$context.requestId",
"apiId" : "$context.apiId",
"resource-path" : "$context.resourcePath",
"resourceId" : "$context.resourceId",
"httpMethod" : "$context.httpMethod",
"sourceIp" : "$context.identity.sourceIp",
"userAgent" : "$context.identity.userAgent",
"accountId" : "$context.identity.accountId",
"apiKey" : "$context.identity.apiKey",
"caller" : "$context.identity.caller",
"user" : "$context.identity.user",
"userArn" : "$context.identity.userArn"
}

10. API Gateway

11. API Gateway Deployment
• Let's ensure the response is correct. Cart Micro Service will
respond as valid JSON.
• Lambda cannot return valid JSON Response.
• Now let's deploy this API, so we can test it! Click the Deploy API
button.

12. Testing
• We should now have a publically accessible GET endpoint.
Ex: https://xxxx.execute-api.us-west-
2.amazonaws.com/prod/cart
• Make sure you add API Key to API Gateway for security
purpose. Each client has to provie x-api-key:xxxxxxxx to
access each REST API's.
• You can access read API as https://xxxx.execute-api.us-
west-2.amazonaws.com/prod/cart/read?loginId=xxxx and
response will be JSON Object like
{ cart:[],
code:200,
loginId:xxx}

13. Latency Performance Checklist
•#1 - Avoid cross-region calls: for best performance, ensure your clients, API, and backend
integrations are located in the same geographical region
•#2 - Lambda functions receiving low traffic may exhibit "cold start" behavior, resulting in a
fraction of requests completing with higher than usual latency. Lambda is constantly trying to
improve cold start times.
•#3 - Ensure your Lambda function has appropriate memory allocation
•#4 - Use resource-based permissions whenever possible. The API Gateway console adds
resource-based permissions to your Lambda function by default. If using STS credentials for your
Lambda or AWS integration, please ensure STS endpoints are activated for the appropriate region
for your account (See
http://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_temp_enable-regions.html)

14. Troubleshooting
• Cloud Watch logs are your friends

15. References
• http://www.slideshare.net/AmazonWebServic
es/a-walk-in-the-cloud-with-aws-lambda-
55789425
• https://aws.amazon.com/dynamodb/
• https://aws.amazon.com/lambda/
• https://aws.amazon.com/api-gateway/

16. Lambda
/CartTasks
DynamoDB
cart
AWS Lambda - Cart Tasks Scheduler

17. Decreased the latency via
keeping the lambda “warm start”
Learning