Galaxy clusters provide crucial information to understand the structure formation of the Universe. Granted by the advanced wide-and-deep surveys in multi-wavelength, cluster science is being explored on the unprecedented scale in the modern times. To this end, one of the most important tasks is to robustly identify galaxy clusters in large surveys with high completeness and purity out to the early Universe. In this talk, I will briefly illustrate the modern optical surveys, especially the Hyper Suprime-Cam (HSC) survey, as well as the data sets that the astronomers are analysing. Next, I will present the current challenges of the cluster science in these large data sets with the goal of having a fruitful discussion with you.