This document discusses designing high-performance middleware for HPC, AI, and data science applications. It provides an overview of the MVAPICH2 project, which develops an open-source MPI library supporting modern HPC architectures and networking technologies. MVAPICH2 aims to provide a converged software stack for HPC, deep learning, and data science through libraries like MVAPICH2, HiDL, and HiBD. The document outlines challenges in communication library design for exascale systems and MVAPICH2's architecture supporting programming models across domains.