Not the person you're asking, but i'm curious what your current approach is. In my first job (ecommerce site) I built a (very slow) recommendation system based

Not the person you're asking, but i'm curious what your current approach is. In my first job (ecommerce site) I built a (very slow) recommendation system based on k-means clustering and it did a pretty good job of clustering customers based on interest and suggesting products, definitely better than random. Building it today would be much faster because there are actually proper libraries/programs for doing this, rather than my inefficient vanilla Python implementation.