IIRC back in symfony 1 part of it was becasue symfony used the first request to write optimized versions of the code into a folder that I cannot remember the name of.
I think there was a way to do this up front in Symfony 1 and there might be some way to do this as part of a build and deploy step. Of course on applications with less traffic and less strict requirements just hooking something up to run a request immediately after deploy might work just as well, but if it runs across n small pods it might be a much better idea to do it on a beefy build machine instead of on n resource constrained pods causing slow loading for n customers.
I think there was a way to do this up front in Symfony 1 and there might be some way to do this as part of a build and deploy step. Of course on applications with less traffic and less strict requirements just hooking something up to run a request immediately after deploy might work just as well, but if it runs across n small pods it might be a much better idea to do it on a beefy build machine instead of on n resource constrained pods causing slow loading for n customers.