Where to set up Phoenix in the request-execution cycle between API gateway and workflow execution?

All the workflows which we write are always placed behind an api-gateway in production. Request Execution Cycle : request -> api_gateway -> workfow execution -> response(sent through API) Now, where should we set up phoenix in the above reques-response lifecycle? I know we need to configure phoenix for every workflow with project name and sessionIDs but where should this go? between api_gateway and workflow execution ?