That made me chuckle. But to be fair, in this case "monolithic" function is just a way to describe this pattern of moving your entire app (express in this case)

That made me chuckle. But to be fair, in this case "monolithic" function is just a way to describe this pattern of moving your entire app (express in this case), inside a Lambda function. When Lambda started to become popular, this was the most common way to migrate to it. Just move your monolithic app to a function, hence "monolithic" functions.