This document provides an overview of a research report by KeyInterval Research about companies' optimal technology stacks (combinations of software/tools) for HR functions. KeyInterval Research surveys HR practitioners to understand their real-world experiences with HR technologies. The report analyzes survey responses from 785 HR practitioners on their use of 13 categories of HR software, including onboarding, succession management, learning management, recruiting, and payroll systems. It finds that the optimal technology stack varies significantly based on factors like company size, region, industry, and individual HR function. The report aims to separate fact from fiction and replace anecdotes with data-driven insights on which HR technologies practitioners currently use and find most effective.