A methodology for the decomposition of the overset grid assembly problem is presented and evaluated. The method is based on identifying grid subsets of a computational domain for which each domain connectivity is calculated individually, and combined at run time to obtain the final complete solution. The proposed method is a framework for the partition of the problem based on the characteristics of the simulation and relies on the user's knowledge of the case, avoiding some of the pitfalls of automatic methods. The methodology was implemented in a computational fluid dynamics solver, allowing the scalable computation of very large simulations of moving bodies, with efficient use of the computational resources. Several examples illustrating the method and the performance improvements with respect to the standard assembly approach are presented.