The Federal Reserve Bank of Boston (Boston Fed) and the Massachusetts Institute of Technology’s Digital Currency Initiative (MIT DCI) are collaborating on exploratory research known as Project Hamilton, a multiyear research project to explore the CBDC design space and gain a hands-on understanding of a CBDC’s technical challenges and opportunities. This paper presents the project’s Phase 1 research. Our primary goal was to design a core transaction processor that meets the robust speed, throughput, and fault tolerance requirements of a large retail payment system. Our secondary goal was to create a flexible platform for collaboration, data gathering, comparison with multiple architectures, and other future research. With this intent, we are releasing all software from our research publicly under the MIT open source license