CLI, SDK , IAM roles

Question 1

What is exponential backoff and when it should be used?

Answer 1

Is a mechanism of retrying API calls that the sleep time between calls increase exponentially. In AWS APIs it is commonly used when ThrottlingException or when 5xx errors are raised.
There is no sense on making exponential backoff on 4xx errors, since it represents a client-side misconfiguration.

Question 2

What is Sigv4 and when it is used?

Answer 2

Sigv4 is a signature method that is used when calling AWS HTTP API to identify the request, using access key and secret key.