Hi @Mark Middlemist ,
I'm glad that you were able to resolve your issue and thank you for posting your solution so that others experiencing the same thing can easily reference this! Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others", I'll repost your solution in case you'd like to "Accept" the answer.
Issue:
You were in the process of devising a partitioning strategy for your SignalR usage on our Azure hosted, multi-tenanted platform.
Your preferred option would be to use a hub per client
You wanted to check if there is a limit on the number of named hub allowed per Azure SignalR service instance but couldn't find the infomation you were looking for in Azure documentation
Solution:
You were informed that "there are no limits to the number of hubs per service instance, but to take into account that there will be 5 server connections per hub, so the more hubs you have, the higher the number of connections, which will therefore impact the required number of units and from there the cost."
If you have any other questions or are running into more Azure SignalR service instance issues, please let me know.
Thank you again for your time and patience throughout this issue.
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Please remember to "Accept Answer" if any answer/reply helped, so that others in the community facing similar issues can easily find the solution.