Senior Fullstack Software Engineer Jobs in Missouri

SMSI Group is a multi-trade mechanical contractor headquartered in Springfield, Missouri, with operations across Missouri, Arkansas, and Oklahoma. We are continually improving how our business operates, and custom software is an important part of that work.

We are looking for a hands-on software developer who can help turn business needs into reliable applications. You will work directly with our IT leadership and employees to understand problems, discuss solutions, and carry projects through development, testing, deployment, and ongoing support.

Our work includes internal web applications, integrations, automation, and improvements to existing systems. An initial priority will be supporting our current Zoho environment while helping build and deploy custom applications that progressively replace its functions. You will also develop other applications as new business needs and opportunities arise.

We use AI coding tools regularly and expect you to use them effectively. You must also have the programming fundamentals to understand the code, make sound technical decisions, and troubleshoot problems independently.

Success in this role means building software that solves practical business problems and remains dependable after launch. You will contribute ideas during planning, deliver tested changes, and help employees adopt and use the applications you build.

Compensation will be determined based on the candidate's experience and qualifications.

$85,000 - $100,000 yearly

• Participate in meetings with business users to understand workflows, clarify requirements, identify exceptions, and recommend practical solutions.

• Build and maintain complete web applications, including user interfaces, backend services, databases, and integrations.

• Take responsibility for assigned projects from initial requirements through production deployment and continued improvement.

• Use AI coding tools to accelerate development while reviewing, understanding, and testing the code they produce.

• Test backend logic, APIs, database operations, permissions, integrations, and failure scenarios, along with the user-facing experience.

• Deploy applications to SMSI-managed environments and troubleshoot issues in production.

• Support and improve our existing Zoho applications, workflows, forms, approval rules, and integrations while replacement systems are developed.

• Help plan and execute migrations, including moving data, validating results, transitioning users, and retiring replaced functionality.

• Maintain clear source control, technical documentation, and deployment instructions so others can understand and support your work.

• Communicate progress, raise issues early, and help balance new development with application support and changing priorities.

• At least three years of professional software development experience, with examples of applications or substantial features you personally helped deliver to production.

• Experience working across the full application stack, including frontend development, backend logic, relational databases, and APIs.

• Strong programming and debugging skills, including the ability to write and troubleshoot code independently of AI tools.

• Practical experience using AI coding assistants, with the judgment to evaluate their output and recognize incorrect or incomplete solutions.

• Experience with SQL, REST APIs, authentication, authorization, and third-party integrations.

• Experience using Git and deploying and supporting software used by real business users.

• The ability to turn an incomplete or evolving business request into a clear development approach.

• Clear communication with nontechnical coworkers and a willingness to learn how the business operates.

• The ability to work independently, ask for input when needed, and follow through after an application goes live.

• Willingness to learn and support Zoho during the transition to custom applications.

Preferred experience

• Next.js, Node.js, and PostgreSQL.

• Railway, Cloudflare, GitHub, and Claude Code or similar tools.

• Zoho Creator, Deluge, Zoho Books, or Zoho Desk.

• Sage Intacct or other accounting and ERP integrations.

• Webhooks, OAuth, and Microsoft 365 or Microsoft Graph integrations.

• Data migration and replacing existing business systems.

• Construction, mechanical contracting, manufacturing, or field-service operations.

• Prior Zoho or Deluge experience is helpful but is not required.

We are particularly interested in the scope of your personal responsibility: what you designed or built, how you tested and deployed it, and how you supported it afterward. Relevant experience may come from a development team, a smaller company, consulting, or your own production applications.

With your application, please include a brief description of one or two applications or substantial features you helped bring to production. Explain your responsibilities, the technologies you used, how you used AI if applicable, and how you handled testing, deployment, and support. Public repositories or demonstrations are welcome but are not required; we understand that much professional software is confidential.

SMSI is dedicated to providing the highest quality mechanical services performed in an honest, dependable, and efficient manner. SMSI offers lots of room to grow in a fast-paced company. We have been serving commercial and industrial markets for 30 years.