Interface optimization is provided using a closed system in which all the individual software components in the system are known to the compiler at a single point in time. This knowledge enables significant opportunities to optimize the implementation of interfaces on a set of implemented objects. When code is compiled, because the compiler knows the full list of interfaces and the objects which implement the interfaces, it can improve execution and working set (i.e., recently referenced pages in a program's virtual address space) when implementing the interfaces on objects. This improvement may be realized by reducing the size of interface lookup tables which map each interface to the object types which implement that particular interface.