I currently have a Web hook that's calling AWS API Gateway -> AWS Lambda function proxy. I'd like to make the web hook more responsive and return an early reply while continuing processing in the Lambda.
I went ahead and did this early reply from the Lambda (Node v6.10) but it didn't appear to have improved responsiveness. Is API Gateway somehow waiting for the Lambda to finish executing despite having the response from the callback already?
The other idea is to post an SNS notification from Lambda and have a second Lambda listen and continue processing but would rather avoid that complication if there's a simpler way.
API Gateway currently only supports synchronous invocation (aka InvocationType: RequestResponse) of Lambda functions, so yes, it is waiting for the full response from the Lambda.
To support your use case, you could use SNS or an another intermediary AWS service like Kinesis, SQS, etc. But you could also do it with Lambda alone. Have the first Lambda function trigger a second Lambda function asynchronously with InvocationType: 'Event', this will achieve the effect you desire.
See this post for more details: https://stackoverflow.com/a/31745774/5705481