Senior Software Engineer ( C++/Golang/Java) in Belfast

Mid‑to‑senior / principal‑level software engineering role in a mission‑critical global telecoms infrastructure business. Open to strong engineers from C++, Java, or Golang backgrounds; problem‑solving mindset valued over language syntax.

Software runs directly on tier‑1 mobile operator networks globally: EE UK, AT&T, and others. Belfast‑based, hybrid working: approximately 2 days per week in office. Salary £55,000-£70,000, with exceptional profiles considered above band.

About the Company: Our client is a global technology business operating at the heart of mobile network infrastructure. Their software runs directly on tier‑1 operator networks worldwide; a code failure means millions of subscribers lose cellular data access instantly. This is engineering where scale, reliability, and precision are operational requirements. The division is the highest revenue‑generating and fastest‑growing within the wider organisation, with 18‑to‑24 months of clear roadmap visibility and a strong commercial pipeline backing continued growth.

The Role: This is a hands‑on engineering position contributing to both core feature development and test automation infrastructure. The team is re‑architecting foundational product lines to natively support 5G and 6G networks, building new fraud detection modules in Go from scratch, and expanding into Machine Learning‑driven network congestion forecasting. AI is deeply embedded in daily engineering practice, used for code review, documentation generation, and diagnosing complex performance issues. Experienced engineers are valued specifically for their ability to guide and direct AI tooling with precision. Whether working independently or as part of a larger group, you will have real ownership over how problems are solved.

Key Responsibilities:

• Design and develop server‑side features across high‑throughput, low‑latency Linux environments.
• Contribute to test automation infrastructure alongside core feature delivery.
• Support re‑architecture of foundational platform products to natively support 5G and 6G network requirements.
• Build and maintain containerised, microservices‑oriented systems using modern CI/CD pipelines.
• Apply AI tooling effectively across code review, documentation, and complex bug diagnosis.
• Collaborate across a distributed engineering team to maintain the reliability standards required for tier‑1 operator deployments.
• Contribute to fraud detection and network congestion forecasting modules where machine learning intersects with systems engineering.

What You’ll Need:

Essential:

• Strong commercial background in server‑side software engineering – C++, Java, or Go all considered.
• Solid understanding of Linux environments: high‑performance, high‑throughput, low‑latency systems.
• Robust grasp of networking protocols: Sockets, TCP/IP, UDP, HTTP, HTTPS.
• Experience with containerisation, microservices architecture, and CI/CD pipelines.
• Strong problem‑solving skills and proven ability to navigate uncertainty and technical unknowns.
• Based in Northern Ireland, eligible to work in the UK permanently and full‑time.

Desirable:

• Low‑level network packet processing experience.
• Background in fraud detection, compliance, or network performance domains.
• Experience integrating or directing AI tooling within an engineering workflow.

Why Apply?

• Salary £55,000-£70,000, with scope to discuss exceptional profiles above band.
• Hybrid working: approximately 2 days per week in the Belfast office.
• Software that runs on tier‑1 global mobile networks: genuine engineering consequence.
• Active expansion into 5G/6G, fraud detection, and machine learning‑driven forecasting.
• AI deeply embedded in daily engineering practice as a force multiplier, not a replacement.
• Funded by the strongest commercial pipeline in the organisation: clear 18‑to‑24 month visibility.
• Lean, candidate‑friendly interview process: one structured interview, no take‑home tests.