AWS Lambda's main function is to reuse the resources.If it creates an EC2 Server for each request then it will soon become a performance concern.Therefore, it will not create an EC2 server for each request so that will not be a performance concern.
Also, you should note that the disk space provided for your function does not clean up properly sometimes as the majority of users reported.
You may read more about the execution lifecycle of Lambda here:
https://docs.aws.amazon.com/lambda/latest/dg/running-lambda-code.html