A bit of context from the original community mail list post, "it supports post mortem debugging by saving a zipped execution context onto S3. This is particularly satisfying as at a recent serverless conference (JeffConf) there was a panel where poor development tools on serverless platforms was highlighted as a real problem.

Debugging something short lived like a Lambda execution is quite startling, as the current answer is 'add more logging', and we all know that sucks. To this end, I’ve created a little screencast showing this in action - and it was pretty cool because it was a real example I encountered when I got everything working and was trying my test application out."

@2:17 "PharoLambda has serialized the execution context of its application and saved it into [my S3 bucket] ... [then on my local machine] rematerializes a debugger [on that context]."