It can be. We run dynamic image resizing (have a couple million image high quality originals in S3, and customers request sizes based on their screen). Each request is handled by a lambda, and even though these are memory intensive operations we never need to worry about servers or running out or RAM or circuit breakers or anything. Whatever the load it just works. The actual operations take on the order of 100ms, so the cold start is negligible to us. And the end product is cached on a CDN anyway. Costs less than one m5.large, but at peak loads it does work 100 times what's possible on the m5.large.
Say you open a page with a 100 images on it for example. With lambda the all images are resized for you in parallel, so total 100ms. If this was servers, would have to run 100 servers to give you the same performance. A single servers could resize images in sequence all day and might be cheaper than running a lambda repeatedly all day, but that's not the requirement. The requirement is to suddenly do 100 things in parallel within 100ms just once when you open the app.
> Say you open a page with a 100 images on it for example. With lambda the all images are resized for you in parallel, so total 100ms. If this was servers, would have to run 100 servers to give you the same performance
You're probably just simplifying, but to clarify servers can totally do multiple things at once. That's how Amazon runs multiple lambdas on one physical server.
They can, and these are already multi core operations. If takes 4 cores 100ms to do this operation, so on a server with 4 cores doing a 100 of them takes 10 seconds, while on lambda it takes only 0.1 seconds to to them all in parallel.
Say you open a page with a 100 images on it for example. With lambda the all images are resized for you in parallel, so total 100ms. If this was servers, would have to run 100 servers to give you the same performance. A single servers could resize images in sequence all day and might be cheaper than running a lambda repeatedly all day, but that's not the requirement. The requirement is to suddenly do 100 things in parallel within 100ms just once when you open the app.