What is the optimal way to deploy Java AWS Lambda?

Question

There are two approaches of "deploying" a Java Lambda:

• create a "fat" jar including all (unpackaged) dependencies, e.g. by use of the maven-shade-plugin
• create a zip file containing my code and a lib directory with all dependencies as jar files

As it takes really long until the environment that executes our simple Lambda is "booted" (20-30s), I wonder if either approach is "faster" than the other or can be further speed up?

Answer 1

I have found that the FAT jar is the optimal approach for lambdas with a footprint smaller than the MB limit. If you are over the MB limit, add the libraries to the lambda's lib folder and read them in.

With jars in the lib, I have found is that the lambda loads a little slower when it launches the first time in a container... the first time it is slower, subsequent launches in the same container are very fast... if it goes to a new container, one-time slow again.

Here is some good info on those cold starts: https://hackernoon.com/im-afraid-you-re-thinking-about-aws-lambda-cold-starts-all-wrong-7d907f278a4f