Sr Full Stack SW Engineer

Connexion Systems + Engineering; Marlborough (MA); On-site; USD 160,000 - 180,000; Full time

Job summary

Connexion Systems & Engineering Inc. seeks a Senior Full Stack Software Engineer in Marlborough, MA to design and implement scalable web and mobile applications. You will work with C#/.NET, modern front-end tech including Blazor, and collaborate with architects to realize product visions.

You will mentor engineers, lead code reviews, and help enforce secure-by-design practices, while integrating APIs to device controllers and ensuring CI/CD and robust testing in regulated medical-device contexts.

Qualifications

• Bachelor's degree in Computer Science, Software Engineering or a related field, or equivalent experience.
• 5+ years of experience in development, full-stack with a focus on front-end and service development.
• Web and mobile application development, with modern front-end technologies and frameworks ideally including Blazor.
• Experience developing solutions using C#/.NET and HTML/CSS/JS or TypeScript.
• Experience in web service and API development, including service-to-device communication and API design.
• Extensive knowledge of object-oriented programming and software engineering patterns such as MVC, MVVM and Dependency Injection.
• Knowledge of version control systems (Git) and Agile methodologies, with experience working in a Scrum environment.
• Working knowledge of medical device software development and standards, including IEC 62304 with experience authoring design control and traceability documentation.
• Understanding of agentic AI development practices, including retrieval, tool use, guardrails, evaluation and the risks of non-deterministic behavior in regulated products.
• Excellent problem-solving skills and a proactive attitude in tackling development challenges.
• Strong verbal and written communication skills, with the ability to collaborate effectively in a team environment and mentor others.
• Experience with cloud platforms such as Azure, AWS or Google Cloud, containerization and CI/CD pipelines
• Solid understanding of cybersecurity principles and the Secure SDLC, including OWASP ASVS, threat modeling, dependency and secret scanning, and software bills of materials.
• Experience with embedded or device integration, including firmware interfaces, device communication protocols and hardware-in-the-loop testing.
• Exposure to embedded or firmware development (C/C++, RTOS, device communication protocols) and hardware-in-the-loop testing.

Responsibilities

• Design and develop responsive, user-friendly applications and services using modern front-end and server-side technologies.
• Collaborate with UX/UI designers to translate designs and prototypes into high-quality, accessible code.
• Implement APIs and services to support communication to device controllers and connected medical devices.
• Optimize applications for maximum speed, scalability and reliability.
• Troubleshoot and debug complex applications across the full stack.
• Write clean, efficient and well-documented code, and help develop strong coding standards and best practices.
• Lead code reviews and mentor less experienced engineers.
• Ensure the technical feasibility of UI/UX designs.
• Apply secure-by-design and secure coding practices, including threat modeling, vulnerability remediation and software supply chain integrity.
• Integrate automated tests into CI/CD pipelines and support verification and validation activities for regulated medical device software.
• Evaluate and integrate agentic AI capabilities, including tool calling, retrieval-augmented generation, guardrails and human-in-the-loop review, supported by appropriate evaluation and observability.
• Provide supporting design documentation and traceability artifacts.
• Stay up to date with emerging trends in web, application and AI development.

Skills

C#

Blazor

Web & mobile development

API design

Cloud platforms (Azure/AWS/GCP)

CI/CD pipelines

Secure SDLC / OWASP

Embedded/device integration

Education

Bachelor's degree in Computer Science or related field

Job description

General Summary

We are seeking a talented and experienced Senior Full Stack Software Engineer to join our dynamic team. The ideal candidate will possess a solid understanding of software engineering patterns and principles, along with experience in web and mobile application development. Proficiency in C# is a must, coupled with experience with modern front-end and server-side technologies. They will work closely with the development team and software architect to implement the vision for future development, collaborating with stakeholders as required.

Primary Responsibilities

• Design and develop responsive, user-friendly applications and services using modern front-end and server-side technologies.
• Collaborate with UX/UI designers to translate designs and prototypes into high-quality, accessible code.
• Implement APIs and services to support communication to device controllers and connected medical devices.
• Optimize applications for maximum speed, scalability and reliability.
• Troubleshoot and debug complex applications across the full stack.
• Write clean, efficient and well-documented code, and help develop strong coding standards and best practices.
• Lead code reviews and mentor less experienced engineers.
• Ensure the technical feasibility of UI/UX designs.
• Apply secure-by-design and secure coding practices, including threat modeling, vulnerability remediation and software supply chain integrity.
• Integrate automated tests into CI/CD pipelines and support verification and validation activities for regulated medical device software.
• Evaluate and integrate agentic AI capabilities, including tool calling, retrieval-augmented generation, guardrails and human-in-the-loop review, supported by appropriate evaluation and observability.
• Provide supporting design documentation and traceability artifacts.
• Stay up to date with emerging trends in web, application and AI development.

Knowledge/Educational Requirements

• Bachelor's degree in Computer Science, Software Engineering or a related field, or equivalent experience.
• 5+ years of experience in development, full-stack with a focus on front-end and service development.
• Web and mobile application development, with modern front-end technologies and frameworks ideally including Blazor.
• Experience developing solutions using C#/.NET and HTML/CSS/JS or TypeScript.
• Experience in web service and API development, including service-to-device communication and API design.
• Extensive knowledge of object-oriented programming and software engineering patterns such as MVC, MVVM and Dependency Injection.
• Knowledge of version control systems (Git) and Agile methodologies, with experience working in a Scrum environment.
• Working knowledge of medical device software development and standards, including IEC 62304 with experience authoring design control and traceability documentation.
• Understanding of agentic AI development practices, including retrieval, tool use, guardrails, evaluation and the risks of non-deterministic behavior in regulated products.
• Excellent problem-solving skills and a proactive attitude in tackling development challenges.
• Strong verbal and written communication skills, with the ability to collaborate effectively in a team environment and mentor others.
• Experience with cloud platforms such as Azure, AWS or Google Cloud, containerization and CI/CD pipelines
• Solid understanding of cybersecurity principles and the Secure SDLC, including OWASP ASVS, threat modeling, dependency and secret scanning, and software bills of materials.
• Experience with embedded or device integration, including firmware interfaces, device communication protocols and hardware-in-the-loop testing.
• Exposure to embedded or firmware development (C/C++, RTOS, device communication protocols) and hardware-in-the-loop testing.

Salary: 160-180k