Summary We’re looking for an experienced VoIP/OpenSIPS/Cisco CUCM engineer to design and implement FCM-based push notifications for our mobile and web softphone clients. Endpoints are currently registered in Cisco CUCM, with OpenSIPS as the internet-facing SIP proxy. Your job is to design the right architecture (mid-registrar / other), build an on-prem push microservice (Python or Node.js) that uses Firebase Cloud Messaging, integrate it with OpenSIPS/CUCM, and make sure sleeping Android/iOS/Web clients can be woken and receive incoming calls. You’ll also handle end-to-end testing and provide clear documentation and handover.