AWS Lambda: async C# handler

Question

The AWS document states that

Using Async in C# Functions with AWS Lambda

If you know your Lambda function will require a long-running process, such as uploading large files to Amazon S3 or reading a large stream of records from DynamoDB, you can take advantage of the async/await pattern. By creating a handler with this signature, Lambda will execute the function synchronously and wait a maximum of 5 minutes for execution to complete before returning or timing out.

I feel very confused Lambda will

execute the function synchronously and wait a maximum of 5 minutes

When Lambda support up to 15 minutes of processing time. Does that mean if I put async on the handler, I can only process one event in 5 minutes?

@TheGeneral Thanks. I removed the broad part and would ask the AWS support instead. I do have some basic understanding about async in .NET and used both async/non async in Lambda integration. I will create an answer if I can get a definitive one from AWS support — qkhanhpro
This to me was an interesting question I have a feeling the documentation has not been updated and should read: "By creating a handler with this signature, Lambda will execute the function synchronously and wait a maximum of 15 minutes for execution to complete before returning or timing out." — David Webster

qkhanhpro qkhanhpro · Accepted Answer · 2019-01-04T03:33:22

The final answer of AWS support at the time:

The document was not up to date. It should run at maximum 15 minute timeout ( depend on the Lambda function configuration )
The async modifier does not change how AWS behave, they will just await it.
The behaviour diference is only on the .NET side

AWS Lambda: async C# handler

2 Answers