@Kirsten The precise work about how the servers will be set up to ensure the scalability will be done by Glenn Rolland (not in this forum yet) if we get the French client, I shared his profile on Slack. What we came up with until now was more general server capacities depending on how many users.
Here is a visual representation that I did, hope that helps ! https://docs.google.com/document/d/1YcgrY173BTU9dWsn9TUO-c_hWZvNXEOkvb0t2yfYp8c/edit?usp=sharing
And the original calculation based on what Rohan came up with : What infrastructure do I need to run an OFN instance and what are the estimated associated costs?