Expedia Group’s GitOps journey with ArgoCD is a testament to innovation, scalability, and resilience in the face of challenges. Transitioning from KubeFed to ArgoCD, we focused on rigorous scalability testing across hundreds of virtual clusters, provisioned using the open-source tool vcluster. Anticipating potential hurdles, we developed comprehensive test cases tailored to diverse application types. Our testing covered three categories of applications—small (15 resources), large (30 resources), and mixed—each including CRDs and jobs. Through extensive experiments, we ran multiple test scenarios using permutations and combinations of these applications across 300 vclusters, scaling from roughly 1,000 to over 30,000 applications. This initiative culminated in identifying the optimal configurations for key tunable parameters in ArgoCD controllers, ensuring performance and stability at scale.