Connected and autonomous vehicles (CAVs) is currently a hot topic and a major focus in the field of edge computing, and it has created numerous pivotal and challenging research problems. In this paper, we present HydraOne, an indoor experimental research and education platform for edge computing in the CAVs scenario. HydraOne is a hardware-software co-design platform built from scratch based on our experience with the requirements of edge computing research problems. We present the design and implementation details and discuss three key characteristics of HydraOne: design modularization, resource extensibility and openness, as well as function isolation. These will help researchers and students fully understand the platform and take advantage of it to conduct research experiments. We also provide three case studies deployed on HydraOne to demonstrate the capabilities of our research platform.