The overnight U.S. Treasury repo market has experienced remarkable growth, with underlying transaction volumes for the Secured Overnight Financing Rate (SOFR) expanding from around $1 trillion in early 2022 to $3 trillion today. At the same time, this essential component of the financial system has become increasingly complex, with new segments introduced as market participants adopt central clearing. This article discusses a simplified framework to understand the complex mechanics and flows of the evolving market. This concept, referred to as the Client Segments Framework, helps the Open Market Trading Desk at the New York Fed (the Desk) monitor the repo market, an important market for the transmission of monetary policy, and report conditions to key stakeholders.