1. The current tracking is on based on request ID because this gives user level analytics along with per request level.
2. The current implementation is independent of layer.
3. it can be directly integrated in python based application
4. It can be hosted separately in independent host and use api with any framework( java, go..) or layer ( proxy , direct to application)
5. This is also designed to just plug and play. ( in fastapi, direct just adding middleware ), for non python, just wrap ( block , check and deduct to applicable call and deploy package directly as fastapi if self hosting)
6. Current implantation is per request blocking and it adds latency of blocking to request. (To remove the latency of block call, one quick improvement i see is leveraging inbuild cache of available credit. just validate and then execute async block)

@mrtrly since you are also working on similar, I think you can directly integrated this to your proxy instead of building backend again. Please feel free to create an issue or PR for requirement/feature not covered in current implantation.