Senior Software Engineer (C++ & C# / Mission-Critical Systems)

Your mission
Are you passionate about writing clean, high-quality code and building reliable software solutions? We are looking for a
Senior C++ & C# Developer
to join our growing development team in
Budapest
, working for a
multinational leader in the telecommunications sector
. In this role, you’ll contribute to cutting-edge projects that power secure and efficient communication systems across the ​Globe.
Your profile
Role Overview
We are looking for a strong engineering talent with solid C++ foundations who is also open to working in C#/.NET. Our Core Communication System (CCS) is implemented in C++ and runs in Linux-based environments. Currently, this domain is owned by a single senior engineer — we are looking for someone who can grow into this system, learn its architecture deeply, and gradually take ownership.
When C++-focused development is not the primary priority, the role actively contributes to our C#/.NET-based backend services within our broader digital services and microservices ecosystem.
This role is ideal for an engineer who enjoys low-level systems thinking (C++) as well as modern backend development (C#) and wants to operate across platform boundaries.
Product & Platform Context
1.
Core Communication System (C++ / Linux / Embedded-like environments)

• Telephony (PSTN) and VoIP systems
• Supervision, lawful interception, recording
• Device management & hardware integrations
• Build systems (CMake), Debian/Ubuntu environments

2
. Digital Services Ecosystem (C# / .NET / Microservices)

• Distributed backend services
• Financial systems (wallets, billing, invoicing)
• APIs and integrations
• Azure-first cloud transformation (hybrid environment)

Key Responsibilities

• Contribute to the evolution and stabilization of our C++-based Core Communication System
• Gradually learn and take ownership of complex C++ modules running in Linux environments
• Collaborate on architecture decisions across C++ and C# domains
• Design and implement backend services using C# / .NET
• Contribute to microservices architecture and domain-driven design initiatives
• Integrate APIs and external systems
• Participate in CI/CD and DevOps improvements
• Ensure high reliability, performance, and security standards
• Support modernization efforts across legacy and distributed systems
• Collaborate closely with DevOps, QA, Product and other engineering teams

Required Qualifications & Experience
Core Engineering Foundation

• 4+ years of professional software engineering experience
• Strong computer science fundamentals (algorithms, data structures, system design)
• Ability to independently design and implement complex modules
• Strong analytical and problem-solving skills

C++ Domain

• Solid experience in modern C++ development
• Experience working in Linux environments (Debian/Ubuntu)
• Familiarity with CMake or similar build systems
• Understanding of system-level programming concepts, performance, memory management
• Openness to deeply understand and evolve an existing complex system

C# / .NET Domain

• Experience with C# and .NET (<ASP.NET> Core or similar)
• Experience building APIs and backend services
• Understanding of service-oriented or microservices architectures
• Database design experience (relational preferred)

Engineering Mindset

• Strong ownership mentality
• Curiosity toward modern technologies and AI-assisted development
• Comfortable working in hybrid (cloud + on-prem) environments
• English proficiency (written and spoken)

Advantages
-
Experience with VoIP technologies (SIP, RTP)

• Experience with Qt framework or embedded Linux
• Experience with Azure cloud services
• Exposure to financial or billing systems
• Experience with DevOps automation tools
• Knowledge of Domain-Driven Design
• Experience working in regulated or mission-critical environments

Why us?

• Work on mission-critical systems with real societal impact
• Own and evolve a strategically important C++ platform
• Contribute to a modern C# microservices ecosystem
• Join a high-ambition engineering transformation
• Shape the future of secure communication platform

-
Professional challenges, inspiring diverse tasks

• Structured development process
• M

ulticulture environment

• Home office days
• Relaxed atmosphere, steady, supportive international team
• Easily accessible modern office with good infrastructure
• Complimentary coffee, fruit and snacks