The Wholesale Energy Market Information System (SIMEM for its spelling in Spanish) is the first open data portal specialized for the Colombian electricity market which its main mission is the centralization of information to enable informed decision-making. This work describes the challenges that were overcome during the planning and implementation of the first open data portal developed to meet the needs of the Colombian electricity sector. The platform was released in October 2023. SIMEM has more than 200 datasets and more than 350 variables available for electricity consumption. This website is the place where authorities, universities, and any citizen interested in searching about the data of this fascinating sector. SIMEM responds to the needs of the electricity sector by enabling technologies for processing large volumes of data in machine-readable formats, facilitating the implementation of advanced analytics models. SIMEM also ensures data standardization and quality based on the rules of the Colombian electricity sector. SIMEM is implemented in a data lake that ensures its scalability, guaranteeing the timely publication of new data to inform decision-makers even as the market transitions to intraday rounds