Thanks for posting your question about how to instrument a Lambda function using a Metric Streams integration + legacy method.
Which language is your function? Depending on the language, we may or may not have a layer you can use. Node.js, Python, and Java functions have layers which include a wrapper that loads an agent + Extension that ships payloads (bypassing CloudWatch). Go and .NET functions don’t have a layer with a no-code-change wrapper and agent, but they can use the Extension layer which just has the Extension.
The Extension has these config options:
It’s also a good idea to check your Metric Stream integration to make sure it is working. If it says no metrics have been received, it’s likely due to either a permissions issue: