Ultrafast molecular phenomena, such as inter- and intramolecular energy transfer, play a pivotal role in determining the final functionality of photoactive biochemically-relevant systems. Photosynthesis is a notable example [1]. Understanding how the natural environment influences the light-induced ultrafast dynamics requires to study the molecules in solution [2]. Our goal is to experimentally examine molecules embedded in water clusters on the femtosecond timescale through time resolved XUV photoelectron spectroscopy [3]. However, the diluted nature of the target samples, leading to low statistics, calls for XUV sources operating in the multi-kHz regime.