Thanks for your interest in Gluu and radius in particular.
The behaviour you are experiencing is expected. Our Radius server which ships with
Gluu CE is single threaded , meaning requests are processed one after the other.
That said , if you need the kind of concurrency you're looking for right now , I would recommend our [radiator](https://gluu.org/docs/gluu-server/4.0/admin-guide/radius-server/gluu-radiator/) plugin. In the upcoming weeks , we will make the radius server that ships with Gluu CE multithreaded. It won't be very high performance , but should work for your use case.
Let me know if you need more questions answered.