[report-to-trees]

In that case you are deploying a whole monolithic app to the Faas platform. This needs to be initialized on every cold start which takes longer the larger your code is. The main selling point (that I have experienced) in Faas is that you can have small, individually scalable functions that are quick to initialize and can be torn down after executing. If you have the whole app under one handler you would be much better off with a different architecture where the app is persistent and always running.

[paulddraper]

That seems like a weird reason.

You can lazy load your route implementations

[report-to-trees]

If you manage to lazy load your routes it may help with cold starts but I think you effectively lose the benefit of warm handlers since every request could use new code that needs to be loaded fresh.

I've never attempted lazy loading inside a Faas platform but I think generally you would be better off creating small deployable chunks and letting the platform handle scaling them up / reusing as necessary. Less fighting against the platform and if you have to maintain strict boundaries to enable lazy loading only the needed code for each route it's a short step to deploying those as their own functions anyway.