Kinetically constrained models are a family of interacting particle
systems used by physicists in order to study the liquid-glass
transition. They are characterized by a very simple non-interacting equilibrium, but their dynamics is slowed down by local kinetic constraints, leading to highly non-trivial behavior of time scales. We will discuss these time scales when adding quenched disorder to the system, focusing on one example of a model on the two dimensional lattice with random constraints.