Building a large-scale, multi-tenant, public, and geo-distributed computing continuum platform that includes both cloud and edge environments, and where any application can be deployed, requires a large amount of computing resources deployed across strategically distributed locations, spanning an entire country or even a continent. One of the challenges to realizing this public computing continuum platform is scalability. To this end, we focus on addressing some scalability challenges and propose a series of solutions. First, we present the meta-federations concept, where many independent local resource providers may lease their resources to multiple fog providers to solve the service coverage and resource utilization issues. We propose UnBound, a scalable meta-federations framework that specifically addresses the difficult multi-tenancy challenges introduced by metafederations. Second, we propose two monitoring frameworks designed for geo-distributed cluster federation environments, Acala and AdapPF, which aim to reduce the cross-cluster network traffic of monitoring while maintaining the accuracy of the monitoring data.