Senior C# / .NET Software Engineer

Festanstellung, Vollzeit · Budapest

Your mission
Are you passionate about writing clean, high-quality code and building reliable software solutions? We are looking for a Senior 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

Duties and responsibilities

  • Design, implement and evolve scalable backend services using C# / .NET
  • Contribute to microservices architecture and domain-driven design initiatives
  • Own features end-to-end from technical design to production rollout
  • Participate in architecture discussions and system evolution decisions
  • Collaborate with cross-functional teams (Frontend, DevOps, QA, Product)
  • Support modernization of legacy components into distributed systems
  • Contribute to API design and internal platform capabilities
  • Participate in improving CI/CD pipelines and DevOps maturity
  • Contribute to observability, monitoring and reliability improvements
  • Ensure high standards of code quality, maintainability and security
  • Support integration with telephony, VoIP, financial and regulatory systems
  • Take part in research and experimentation with AI-based solutions where applicable
  • Mentor junior developers and contribute to knowledge sharing

Required Qualifications, Experience & Competencies

Professional Experience & Skills

  • Core Engineering Foundation
  • 5+ years of professional software engineering experience
  • Strong foundation in computer science fundamentals (data structures, algorithms, distributed systems, system design)
  • Ability to design scalable, maintainable and resilient systems
  • Experience working on complex, mission-critical systems
  • Deep understanding of backend architecture principles
  • Strong API design and service-oriented architecture mindset
  • Experience reasoning about performance, reliability and security
  • Technology Adaptability
  • Proficiency in at least one modern backend programming language (C#/.NET experience is highly valued, but strong engineers from other ecosystems are welcome)
  • Experience working in distributed or microservices-based systems
  • Solid database design knowledge (relational and/or NoSQL)
  • Experience working with cloud environments (Azure preferred, but not mandatory)
  • Comfort navigating hybrid (cloud + on-prem) environments
  • Learning agility and architectural thinking over specific library knowledge
  • AI & Modern Engineering Mindset
  • Interest in applying AI-assisted development practices
  • Openness to integrating AI-driven features into products
  • Curiosity toward automation, intelligent workflows and experimentation
  • Experience using modern AI development tools (Copilot, LLM-based workflows, etc.) is an advantage
  • Growth mindset toward emerging technologies
  • Active contribution to AI-enabled engineering workflows and intelligent product capabilities
  • DevOps & Engineering Culture
  • Understanding of CI/CD principles
  • Ownership mentality and accountability for production systems
  • Experience working in collaborative, cross-functional teams
  • Desire to contribute to high-performance engineering culture
  • English proficiency (written and spoken)

Advantages

  • Experience in telecommunication systems (VoIP, SIP, RTP)
  • Experience in highly regulated environments
  • Experience with financial systems or billing engines
  • Domain-driven design experience
  • Experience contributing to DevOps transformation initiatives
  • Exposure to AI-driven features or experimentation


Why us?

We are offering 

  • Professional challenges, inspiring, diverse tasks
  • structured development process
  • learning path on new technologies (AI, LLM)
  • multiculture environment
  • flexible working hours and home office days
  • relaxed atmosphere, steady, supportive international team
  • easily accessible modern office with good infrastructure
  • complimentary coffee, fruit and snacks
About us
Telio is a medium-sized, internationally active, rapidly growing company in the field of telecommunications and IT services in the prison sector. As the European market leader, we have been providing communications solutions for prisons and their inmates worldwide for over 25 years. With more than 270 employees, we are active in 23 countries and develop, install and operate communication and media systems that make an important contribution to resocialization in prisons as well as in correctional facilities.
Wir freuen uns, von Ihnen zu hören!
Vielen Dank für Ihr Interesse an Telio. Bitte füllen Sie das folgende kurze Formular aus. Sollten Sie Schwierigkeiten mit dem Hochladen Ihrer Daten haben, senden Sie bitte eine E-Mail an jobs.headoffice@tel.io
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