I looked into lambda before...
It turns out that its just a nice little earner for Amazon.
Sure it sounds convenient on the surface, but actually AWS's tools for doing anything useful with it were pretty poor and not easy to get your head around (this was a year ago and may have improved).
Ditch Lambda, set up your own VMs to do what you want and you'll be making a big saving anyway.
Paris, cause well, whats the effing point?