Koupaki worked as an official at the Central Bank of West African States (BCEAO) and the International Monetary Fund (IMF), and he was Director of the Cabinet of the Prime Minister from 1996 to 1998.
Under President Yayi Boni, Koupaki was Minister of Finance from 2006 to 2007 and then Minister of State for the Exploration, Development, and Evaluation of Public Policy from 2007 to 2011.
Under President Patrice Talon, Koupaki has been Secretary-General of the Presidency since 2016.