Comment by coredog64
This is a well known issue, and the fix is not to create any boto3 clients at runtime. Instead, ensure they're created globally (even if you throw them away) as the work then gets done once during the init period. The init period gets additional CPU allocation, so this is essentially "free" CPU.
Source: I'm a former AWS employee.
Thanks for citing your sources, I think your source may be out if date, though! The “free init time hack” was killed in August (unless I’m missing something - never used it myself).
https://aws.amazon.com/blogs/compute/aws-lambda-standardizes...