1. A computer-implemented method for replacing annotated program code in a networked computing environment, comprising: detecting an annotation in a program code file, the annotation comprising a runtime optimization request with a set of criteria for running the program code file; monitoring, responsive to detecting, at least one method in the program code file during runtime based on the set of criteria; identifying at least one substitute program code library based on at least one of: an annotation in a program code file, a selection provided by a user, and a results store, the at least one substitute library being identified from a code repository and stored in a computer storage device; identifying at least one substitute method for the at least one method, the at least one substitute method being identified from the at least one substitute program code library stored in a computer storage device; monitoring the at least one substitute method based on the set of criteria during runtime; and selecting, based on the monitoring of the at least one substitute method, a particular substitute method which best satisfies the criteria of the optimization request from the at least one substitute method for use in the program code file and a particular substitute program code library from the at least one substitute program code library.