A stream processing platform that provides fast execution of stream processing applications within a safe runtime environment. The platform includes a stream compiler that converts a representation of a stream processing application into executable program modules for a safe environment. The platform allows users to specify aspects of the program that contribute to generation of modules that execute as intended. A user may specify aspects to control a type of implementation for loops, order of execution for parallel paths, whether multiple instances of an operation can be performed in parallel or whether certain operations should be executed in separate threads. In addition, the stream compiler may generate executable modules in a way that cause a safe runtime environment to allocate memory or otherwise operate efficiently.