AWS Lambda Java SDK examples.

1 - Synchronous (RequestResponse) Handler

Serverless weather API

• A simple example with CRUD operation to accept request via API Gateway and interact with DynamoDB backend table. AWS services used:
  • API Gateway
    • Lambda authorizer function is used to authentcate request using a token passed from API Gateway.
    • The authorizer function evaluates incoming toekn and returns allow or deny security policy back to API Gateway.
    • If 'allow' return policy is returned from the authorizer function, API Gateway forward the request to a lambda function based on the request resource and method.
  • Lambda
  • DynamoDB

2 - Asynchronous (Event) Handler

• Client will receive 202-Accepted response but not the actual response detail of a function logic. Once processing gets completed, response payload will be sent to a destination:

  • SNS topic
  • SQS queue
  • Lambda function
  • EventBridge event bus
  • Kinesis or DynamoDB stream

• Destinations needs to be configured in the Lambda function config. in AWS Console or using Lambda API.

Send response to a queue (SQS and DLQ)

3 - Stream Processing Handler (TODO)

• The event trigger will be DynamoDB stream (events from CRUD operations on an item).
• Lambda function logic receives the stream event from DynamoDB and executes additional logic. The response can be sent to a destination, if needed.