DevOps IMS Application Service Designer

About Us
T-Digital is the Deutsche Telekom Tech powerhouse in Greece. We create compelling digital propositions for the world's largest Telekom giant by building scalable and agile platforms to provide the best digital experience to Deutsche Telekom customers across Europe. We are an agile and international organization where creativity and freedom are valued the most. We are looking for those who can embrace our culture, think outside the box, and turn ideas into high-quality products and services.

About Our Culture
We strive to build and strengthen a strong culture of caring and performance, creating a workplace we are proud of. We attract good fellas, create life-changing experiences, and believe in work-life balance. What we absolutely need from you is:

• Innovation Focus
• Customer Obsession
• Growth Mindset

Our Guiding Principles

• Delight our Customers
• Get Things Done
• Respect & Integrity
• One Team
• Ownership (I am T – Count on Me)
• Curiosity & Growth

About The Job
The Project: IP Multimedia Subsystem (IMS)-Based Voice & Messaging Services in a Global IoT Context
As IoT expands, voice and messaging services remain critical for scenarios like emergency calling, M2M communication, and network-triggered features. Our team is responsible for the design, automation, and operation of IMS-based services such as VoLTE and SMS over IP for critical emergency service of our automotive and standard customers — ensuring these are seamlessly integrated into DT IoT's global footprint.

We're building highly available, cloud-integrated IMS platforms and application services, with a strong focus on service logic, DevOps enablement, and infrastructure lifecycle management. These services must scale globally, operate with minimal latency, and offer robust interoperability with both legacy and future-ready telecom networks.

The goal of this work is to design IMS voice and messaging services that are cloud-native, automated, and globally deployable, ensuring exceptional reliability, scalability, and performance.

We Do This By Combining

• Deep SIP/IMS application expertise
• Cloud and NFV/virtualized infrastructure
• CI/CD and automation tooling
• End-to-end lifecycle ownership—from service modelling to deployment and continuous improvement

We work as part of a cross-border, skill-based chapter structure, collaborating across 10+ countries to deliver on Deutsche Telekom's technology promise.

What We Will Trust You With
IMS Application Design & Lifecycle

• Design and maintain real-time voice and messaging services over IMS (VoLTE, VoWiFi, SMS over IP, voicemail, supplementary services).
• Define SIP call flows, Application Server (AS) logic, user profile models, and Initial Filter Criteria (iFC).
• Collaborate on interworking with MSS, SBC, MGCF, and ENUM routing for CS core and interconnect support.
• Translate business and service requirements into functional service logic and workflows.

Infrastructure & Service Operations

• Engage in the entire lifecycle of IMS infrastructure and services—from design to deployment and evolution.
• Conduct system design reviews, capacity planning, and go-live support for new features.
• Monitor service availability, latency, and health; proactively address degradations or faults.
• Lead incident response and root cause analysis with deep SIP protocol expertise.

DevOps, Automation & NFV

• Contribute to CI/CD pipelines, test automation, and platform deployment using GitLab, Jenkins, Ansible, Helm, or Tosca.
• Develop and maintain infrastructure as code (IaC) for IMS VNFs/CNFs across OpenStack, VMware, or Kubernetes.
• Automate monitoring, validation, and scaling of IMS services to improve reliability and reduce manual work.
• Support onboarding of IMS/NFV functions, integration testing, and production readiness.

Documentation & Continuous Improvement

• Prepare detailed service models, flow diagrams, and test plans.
• Continuously improve processes for monitoring, testing, and deployment.
• Participate in knowledge sharing, coaching, and creation of technical guidelines.

About You
We are looking for someone who combines
deep IMS/telecom expertise
with a
DevOps mindset
and passion for
cloud-native service design
.

Professional Skills
What you will need:

• Proven experience with Voice Core/IMS design and operations (Huawei or Nokia preferred).
• Strong knowledge of TCP/IP networking, SIP signaling, and security concepts.
• Experience with virtualization and NFV platforms (OpenStack, VMware, Kubernetes).
• Experience with CI/CD and automation tools (GitLab, Ansible, Jenkins, Kubernetes, Maven, Tosca).
• Proficiency in Unix/Linux system administration and scripting.

Specific Knowledge Areas

• IMS architecture (P/I/S-CSCF, AS, HSS, BGCF, SBC, MGCF)
• MSS and R4 voice network components (a plus)
• SIP call analysis tools (Wireshark, Homer, sngrep)
• Public/private cloud deployments and orchestration tools
• Programming knowledge in C, C++, Java, or PHP (a plus)
• NFV onboarding and lifecycle management

Certifications (Preferred)

• CCNA or equivalent
• ITIL Foundation
• Kubernetes/DevOps certifications (e.g., CKA, GitLab CI)

Soft Skills

• Self-motivated and proactive
• Excellent communication in English (written and verbal)
• Highly collaborative, analytical, and problem-solving mindset
• Willingness to travel occasionally as needed
• Ability to handle confidential or sensitive information

About What We Can Offer

• Flexible & remote work options
• Very competitive annual bonus scheme
• Meal vouchers
• Private health insurance
• Modern office spaces in Thessaloniki and Athens
• A new team that will support and challenge you on your path to growth
• Extra days off
• Opportunities to travel and collaborate globally

… and many more

You know the job. We know what you need to do it well.

Let's talk