Senior Fullstack Engineer

Jonas Software; United States; Remote; USD 90,000 - 130,000; Full time

Job summary

Jonas Software is seeking a Client Success Manager to shape our software modernization initiatives and lead technical projects. This role requires a strategic technologist with a strong foundation in both legacy and modern architectures, alongside a passion for mentoring and process improvement. Join a remote-first company committed to empowering membership-based organizations and modernizing solutions for clients.

Qualifications

• 5+ years of experience in a Full-stack role.
• Strong experience with .NET Core, .NET Standard, C#, and Java.
• Frontend experience with JavaScript frameworks (React preferred).

Responsibilities

• Build new functionality while modernizing the core software.
• Collaborate with engineers, product managers, and stakeholders.
• Lead modernization and consolidation efforts across legacy and current platforms.

Skills

Problem-solving

Communication

Attention to detail

Customer service mindset

Education

Bachelor's degree in computer science, engineering, or related field

Tools

.NET Core

Java

Azure DevOps

Git

AWS

Job description

Job Description:

COMPANY

Member Solutions, part of Constellation Software (TSX: CSU), is a leader in billing and member management solutions for membership-based businesses across the United States and Canada. With over 30 years of expertise, we serve hundreds of martial arts studios and support fitness facilities, gymnastics clubs, dance studios, shooting ranges, and more.

At Member Solutions, we don't just provide software. We live by our unique ‘software for life’ philosophy. It’s a commitment to our clients for life. We believe in building long-term partnerships, genuinely understanding their businesses, and empowering them to create stronger communities, one member at a time. As a Client Success Manager, you will be at the forefront of this mission.

Our software products and managed billing services help businesses streamline operations, ensure timely and accurate invoicing and collections, and maintain compliance with relevant laws and regulations.

As a remote-first company with deep roots in Pennsylvania, Member Solutions is rapidly expanding across North America. This growth presents exciting career opportunities for those ready to scale with us.

HOW WE WORK

We like operating at full throttle in a collaborative group of startup veterans and novices who debate the right way to do things and are empowered to take smart risks, find brilliant solutions, and build things that better the well-being of our customers and theirs. We’re doing our best work ever, learning from our mistakes, improving on our successes, and finding abilities we didn’t know we had for using sophisticated logic and business intelligence to make bedrock business principles accessible and intuitive to small and enterprise businesses alike.

WHAT YOU’LL DO

You’ll be responsible for building new functionality while modernizing the core software that powers our business. Expect to work across a mixed landscape of .NET and Java applications—some modern, others dating back 20+ years. This isn’t just about fixing bugs or shipping short-term features. You’ll help define how we rebuild and consolidate systems, leverage AI to speed up delivery, and make architectural decisions with long-term business impact.

You’ll work closely with engineers, product managers, and stakeholders across departments to prioritize the right work and see it through. You’ll need to be hands-on with code while also stepping back to guide long-term strategy. This role requires someone who can operate with minimal direction, move between big-picture planning and day-to-day execution, and consistently deliver real business value.

Your responsibilities will include:

• Design and implement scalable systems using both .NET and Java
• Lead modernization and consolidation efforts across legacy and current platforms
• Use AI tools where appropriate to streamline processes and reduce complexity
• Troubleshoot production issues and support critical applications
• Collaborate with product, support, and other teams to ensure alignment
• Write clean code, and document decisions
• Help grow engineering talent by mentoring others and promoting best practices
• Track and manage your work through Azure DevOps

WHO YOU ARE

You’re a strategic technologist with a systems mindset. You’ve worked on both legacy and modern architectures, and you know when to refactor, when to rebuild, and when to leave something alone. You’re curious about AI and automation, and you’re already experimenting with how they can change the way we build software.

You enjoy mentoring other developers, writing clear documentation, and improving engineering practices. You’re confident working independently, leading initiatives, and making architectural decisions. You don’t get flustered in ambiguity, and you communicate clearly even when things are uncertain.

• Bachelor's degree in computer science, engineering, or a related field
• 5+ years of experience in a Full-stack role
• Strong experience with .NET Core, .NET Standard, C#, and Java
• Frontend experience with JavaScript frameworks (React preferred)
• Deep understanding of relational databases, particularly MSSQL, along with strong DBA fundamentals
• Experience with REST APIs, WebAPI2, JSON, XML, AJAX, and OAuth2
• Familiarity with Agile and Scrum methodologies
• Proficient with DevOps tools and workflows including Git, CI/CD pipelines, and Azure DevOps
• Comfortable working in cloud environments, particularly AWS (Lambda, S3, API Gateway, etc.)
• Exposure to AI tools and frameworks such as OpenAI APIs, LangChain, and vector databases
• Strong written and verbal communication skills
• High-level understanding of IT concepts including infrastructure, security, deployment, and compliance

HOW YOU’LL DO IT

• Strong problem-solving skills
• Good communication skills
• Ability to work under pressure
• Attention to detail
• Customer service mindset

#LI-PP1

Business Unit: Member Solutions - Canada Scheduled Weekly Hours: 37.5 Number of Openings Available: 1 Worker Type: Regular More About Jonas Software:

Jonas Software is the leading provider of enterprise management software solutions to the Country and Golf Clubs, Foodservice, Construction, Fitness & Sports, Attractions, Salon & Spa, Education, Radiology/Laboratory Information Systems, and Product Licensing industries. Within these vertical markets, Jonas is made up of over 65 distinct brands, which are respected and leaders within their own domain.

Jonas’ vision is to be the branded global leader across the aforementioned vertical markets and to be recognized by customers and respective industry stakeholders as the trusted provider of ‘Software for Life’ and as an ambassador for technology, product innovation, quality, and customer service.

Jonas Software is the valued technology partner of over 60,000 customers worldwide in more than 30 countries. Jonas employs over 2,000 skilled individuals consisting of a cross-section of industry experts and technology professionals. Jonas is headquartered in Canada and also operates offices throughout North America, the United Kingdom, Europe, Australia New Zealand and Africa. Jonas is a 100% owned subsidiary of Constellation Software Inc., headquartered in Toronto and traded on the S&P/TSX 60.