Senior Software Engineer | Mainspring

Why This Role Stands Out:

Hi! 👋🏾 We’re Mainspring. Our technology team is growing and we’re looking for a Senior Software Engineer to join us and shape our future.

Most engineers spend years inside massive teams where their work is a small piece of a huge machine. At Mainspring, you’ll see the full impact of your code—helping architect the future of a fast-growing FinTech platform redefining payroll, payments, and time management.

You’ll work directly with our world-class, frontier-thinking CTO—a hands-on leader who’s passionate about mentorship, innovation, and building great software. This is a rare chance to influence architecture, own critical systems, and grow faster than you would anywhere else.

What You’ll Do

  • Lead key modernization initiatives, helping migrate legacy ASP.NET and Clarion systems to a modern .NET Core + React architecture.

  • Design and build scalable APIs and services that power product integrations and SSO authentication across our ecosystem.

  • Collaborate with Product, Design, and DevOps to deliver clean, modular, high-impact features.

  • Establish engineering standards, CI/CD pipelines (AWS, GitHub Actions), and best-practice frameworks.

  • Mentor mid-level engineers and coordinate with distributed teams across the US and India.

  • Drive innovation in data management, performance tuning, and interoperability between

You Might Be Our Person If…

  • You’ve got a high school diploma or equivalent required; associate or bachelor’s degree preferred. And at least 2+ years of payroll or timekeeping system experience (ADP, Kronos, Paycom, or similar preferred).

  • You’re an expert in knowledge of federal, state, and local wage and hour laws.

  • Organization and strong attention to detail is your thing. You’re the first person who catches a typo or missing number. You cross the T’s and dot the I’s with the best of them.

  • You communicate in a succinct and clear manner. You know how to synthesize and translate information in a way that just makes sense. When you engage with customers they feel supported and encouraged.

  • You have the ability to handle sensitive information with discretion and confidentiality

  • You have solid technical acumen; proficiency in Microsoft Excel, G-suite, and other standard office software.

What You Bring

  • 6+ years hands-on experience with C#, .NET Core, SQL Server, and RESTful APIs.

  • Strong frontend experience (React preferred; Angular/Vue also welcome).
    Proven success in modernizing legacy systems or migrating monolithic apps to microservices.

  • Skilled in AWS (EC2, RDS, S3, Lambda) and CI/CD tools (GitHub Actions, Jenkins).

  • Understanding of SSO, OAuth, JWT authentication flows.

  • Solid software design and TDD fundamentals; balanced pragmatism and vision.

You might be our person if you have...

  • Experience with Clarion, Telerik, or other legacy frameworks.

  • Familiarity with HRIS / Payroll / Workforce Management systems.

  • Knowledge of data warehousing, analytics, or AI-assisted engineering.

The Deal

  • Compensation: $160k - $175k

  • Work remotely

  • Health Insurance

  • Culture: Zero red tape, zero politics. High ownership, high candor, big wins.

How to Apply

Our team will take time and care to review each application. If we’re interested, we’ll respond and book your first call within 1-2  business days.

Ready to flex your talent without micromanagement? Let’s talk.

To Apply:

Send your resume to

shoshana@themainspring.ai