Thanks for posting your question in the Microsoft Q&A forum.
Azure Service Bus: Service Bus is a fully managed enterprise message broker service, it supports queues and publish-subscribe topics for decoupling applications and services and you can create a Service Bus namespace in one resource group and access it from Functions in another resource group.
Azure Functions EP2 Plan: EP2 is part of the Elastic Premium plan, offering more powerful compute and longer running times than consumption plan, Functions on EP2 can be deployed across different resource groups while still using the same plan.
The plan itself exists in one resource group, but Function Apps using that plan can be in other resource groups.
While it's possible to spread resources across resource groups, it's generally simpler to manage if related resources are kept in the same resource group, ensure you have a clear naming convention and documentation to keep track of which resources are where.
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