Full Stack Software Developer

This role helps establish Built by Mainstreet:

Mainstreet is building an internal software development capability. This role is for a practical full stack developer who wants to build real applications, support them in production, and help shape how software gets built inside a Microsoft-based financial institution. Built by Mainstreet exists to solve internal business problems with software we can understand, improve, reuse, and support ourselves. We use modern tools, including AI-assisted development, to build software faster and more accurately. This is the first dedicated software development hire in Built by Mainstreet, so the role also helps establish practical, repeatable development standards as the capability matures.

You will turn internal workflows into reliable software products:

As our Full Stack Software Developer you will build, deploy, and maintain internal software applications for Mainstreet Credit Union. You will work within a primarily Microsoft technology ecosystem. C#/.NET is our preferred application development stack, with PowerShell used extensively for scripting, automation, and environment administration. You will take applications from prototype through production for tools that support member origination, lending analysis, and staff operations. You will work with business analysts, business users who create prototypes or workflow tools, Business Intelligence, and department leaders to turn real workflows into reliable, secure products that meet our data handling and access control expectations. You will work with the Technology Architect and Systems Administrator on platform patterns, security and integration approaches, Active Directory and Microsoft Entra ID integration, and production environment configuration.

Success in your first year means you have taken ownership of at least one application end to end, including code, testing, deployment, documentation, monitoring, and support. You contribute to a working application pipeline and documented deployment process. You help mature practical standards for Git-based source control, code review, automated builds and tests, CI/CD, deployment, documentation, support, and general development practices. You respond to staff-reported issues with reliable triage and resolution cadence. You leave the codebase and operating model clearer, safer, and easier to maintain.

You will work with support across business, data, infrastructure, and architecture:

You will not be expected to own every infrastructure, security, database, or business domain decision independently. You will work with the Technology Architect, Systems Administrator, Business Intelligence, business analysts, and business teams to make practical decisions and build reliable software within shared standards. The Technology Architect will set the overall architecture, platform patterns, engineering standards, security and integration approaches, and technical direction. You will own implementation and day-to-day software engineering within those patterns, while contributing practical feedback as the standards evolve.

Major Duties and Responsibilities:

Application Development:

• Build web applications using C#, ASP.NET Core, and Blazor against a REST API backend.
• Implement data models, business logic, and API endpoints following clean architecture principles.
• Build and maintain application database schemas using Entity Framework Core migrations against SQL Server, with Azure SQL or other approved data platforms used where appropriate.
• Integrate applications with internal APIs, vendor APIs, CGI RFS 360, credit bureau services, e-signature platforms, Microsoft 365 and Teams, existing SQL data sources, legacy applications, identity services, and AI-assisted development or large language model APIs where they support practical application delivery.
• Work collaboratively with Business Intelligence and the Technology Architect/SQL Administrator when designing application databases, integrating with existing data sources, and developing or optimizing production SQL queries.
• Write unit and integration tests and maintain test coverage across Core, Infrastructure, and API layers.

Deployment and Operations:

• Contribute to the development and improvement of Git-based source control, code review, automated build, testing, and CI/CD practices for internal application projects.
• Deploy and support applications primarily within Mainstreet’s Windows Server/IIS environment, with the ability to support cloud-hosted platforms such as Azure App Service where appropriate.
• Manage application secrets and configuration using approved secure mechanisms appropriate to the hosting environment, with no secrets stored in source-controlled code or configuration. This may include environment-level configuration and cloud secret-management services such as Azure Key Vault where appropriate.
• Coordinate releases through dev, test, and production environments with documented rollback steps
• Monitor application health, review logs via Serilog, and respond to alerts?

Security and Compliance:

• Apply least-privilege access controls using the authentication and authorization approach appropriate to the application and hosting environment, including Active Directory, Windows Authentication, Microsoft Entra ID, security groups, and role-based authorization.
• Ensure sensitive member and financial data is encrypted in transit and at rest.
• Conduct or coordinate static code scanning on every change, triage and fix flagged dependencies. 
• Maintain audit logs for access, data changes, and key workflow events.
• Support periodic security reviews and penetration testing as required by Mainstreet’s security policy.

Maintenance and Support:

• Triage and fix production issues raised by staff or end users.
• Manage database migrations safely in production in collaboration with Business Intelligence and the Technology Architect/SQL Administrator where production data design, performance, security, or operational considerations are involved.
• Keep dependencies, SDKs, and packages current.
• Apply critical security patches within defined service levels.
• Maintain technical documentation for deployed systems, including architecture, runbooks, and environment setup.

Qualifications and Experience:

Required qualifications

• Post-secondary education in Information Technology, Computer Science, or equivalent experience.
• 3+ years of professional software development experience.

• Proficiency in C# and .NET.
• Experience building ASP.NET Core Web APIs.
• Working knowledge of Blazor Server or a comparable component-based UI framework, or the ability to learn Blazor with support.
• Entity Framework Core experience with schema design, migrations, and query optimization.
• SQL experience with SQL Server or Azure SQL.
• Working knowledge of the Microsoft technology ecosystem, including SQL Server, Git, and secure application development practices.
• Git experience with branching, pull requests, and code review.
• Awareness of secure coding practices including OWASP Top 10, input validation, and secrets management.
• Ability to read, extend, and pragmatically modernize an existing codebase without requiring a full rewrite, while preserving functionality that already works.
• Practical C# and .NET judgment to own day-to-day software engineering decisions within platform patterns, engineering standards, security approaches, and technical direction established with the Technology Architect.
• Comfort using modern AI-assisted development tools as part of a normal workflow while reviewing, testing, and taking responsibility for the resulting code.
• Comfort working as an early hire in a new internal software development capability and helping establish practical standards for source control, testing, CI/CD, deployment, documentation, support, and maintainable development practices.
• Ability to move between business requirements, code, deployment, documentation, and support.
• Clear communication with non-technical colleagues, independence as a strong intermediate developer, and practical judgment to avoid over-engineering.

Preferred qualifications

• Experience in a regulated environment such as financial services or healthcare.
• Microsoft Fluent UI for Blazor or equivalent component library experience.
• Familiarity with REST API design and OpenAPI or Swagger documentation.
• Structured logging experience with Serilog or similar tools.
• Experience reading production logs to diagnose issues.
• Exposure to AI or large language model API integrations such as Anthropic, OpenAI, or Azure OpenAI.
• Understanding of core banking system concepts or data models.
• Experience with xUnit or NUnit and integration test patterns.

Compensation and Benefits

Salary Range: $84,788.00.00 - $105,985.00.00 (commensurate with experience)

Bonus:  Eligible for a discretionary annual bonus based on individual and organizational performance.

Mainstreet also offers its employees:

• Mainstreet is a Living Wage employer
• Opportunity to work at a values-based cooperative
• Work-life balance and flexible work arrangements
• Generous vacation and benefit packages 
• Opportunities for training and advancement

Join Mainstreet Credit Union and be part of a workplace that values diversity, promotes equity, and fosters inclusion. We actively seek diverse perspectives, ensure equal opportunities for all, and cultivate a culture where every individual feels valued. Our commitment to continuous learning ensures an environment where everyone can thrive.

Mainstreet Credit Union is an equal opportunity employer. We welcome applications from candidates of all backgrounds and experiences. Accommodation is available upon request for candidates taking part in all aspects of the selection process.

Application Instructions

Applications can be submitted via Mainstreet's website at:   Careers | Mainstreet Credit Union

*Note: This posting is for an open vacancy. Application compatibility assessed with AI.