Lumigo turns ThrottlingException into InvalidSignatureException

[alexbepple]

Describe the bug
While investigating aws-lite/aws-lite#127, we stumbled upon weird behavior caused by Lumigo that we cannot explain and that looks like a bug. We have a situation in which we exceed the SSM rate limit and get a ThrottlingException, upon which the client retries. Without Lumigo, the retries also return a ThrottlingException. But with Lumigo, the retries look like InvalidSignatureException.

To Reproduce
Steps to reproduce the behavior:

1. Deploy https://github.com/heartstocks/aws-lite-InvalidSignatureException.
2. Add > 20 SSM parameters prefixed with '/ArcAwsLiteInvalidSignatureExceptionStaging/' in order to increase load on SSM Param Store.
3. Provoke ThrottlingExceptions by calling the Lambda with many users at the same time, e.g. k6 --vus 200 --iterations 200 …
4. Connect AWS Account to Lumigo and enable tracing by clicking the toggle in the Lumigo dashboard.
5. Repeat step 3. The initial ThrottlingException can still be seen, but the retries now appear to receive a InvalidSignatureException.

Here are the logs for comparison:

• log-events-viewer-result.no.lumigo.csv
• log-events-viewer-result.with.lumigo.csv

Expected behavior
Even with Lumigo tracing the Lambda, ThrottlingException should be shown.

Runtime details

• Lambda runtime: Node.js 20.x, Architecture: arm64
• Lumigo layer version: 260

Additional context
As you can see from the screenshots in aws-lite/aws-lite#127, the issue not only affects SSM Param Store, but also DynamoDB access.