Or plan only affect the read write operation no matter how many users make the request
and is there any cap of highest users can be served at the same time
Fauna doesn’t use traditional, long-running connections. All queries are made via HTTP requests, so there is no limit to the number of concurrent users.
If the number of simultaneous connections approaches the maximum that can be served, we deploy more nodes to service the load.
the maximum should be the global of faunadb server but not just only my app. Right?
Yes, your app is not limited by the number of concurrent connections.
It’s already answered that there’s no limit on concurrent users.
Your app may be limited by number of concurrent write operations to a single document. That is, two writes cannot happen at the same time due to (strict) serialization, so they get queued and retried, but there are limits.
This means you can have unlimited users, but if you give all of them the power to modify the same document, and then they all try to do so at the same time… that will cause problems.