Last year I built a multitenant system for my employer Spatialest. It was my first time doing a multitenant system, so I researched a lot before doing it. I studied carefully the experience of platforms like Shopify, as their multi tenant requirements were similar to ours. But even after some careful study, I made some mistakes. One of those mistakes is what I’ve come to call tenant pollution. This means that many services or routines need the tenant as an argument in order to do something.