Senior Backend Developer / C#, ASP.NET, MySQL / Hollywood, FL

Job Description
A growing fintech company is seeking a Senior Backend Developer to help architect, build, and scale its core business platform. The company's primary in-house application is built on an ASP.NET 8 monolithic architecture backed by a MySQL database. This role will play an important part in developing new business functionality while helping modernize the existing platform through the gradual decomposition of legacy modules into independently deployable ASP.NET Core services.
The ideal candidate is a highly experienced C#/.NET backend developer with a strong background in scalable software architecture, API development, SQL performance, and automated testing. You will work closely with product, engineering, and business stakeholders to translate requirements into reliable software and help establish strong engineering practices across the codebase.
Required Skills & Experience

• 6+ years of professional C# and ASP.NET development experience.
• 5+ years of experience working with SQL databases.
• Strong background building and maintaining large-scale, scalable software applications.
• Experience defining service contracts, functional expectations, and testing boundaries.
• Proven ability to introduce and expand automated testing practices in codebases with limited existing test coverage while maintaining development velocity.
• Proficiency in:
  
  • C#
  • Backend API development
  • .NET Core 7+ (Dependency Injection, Configuration, and Logging)
  • ASP.NET Core, MVC, and WebAPI
  • Dapper and Json.NET
  • HTTP, REST, and JSON
  • SQL databases, particularly MySQL or MSSQL

Desired Skills & Experience
Familiarity with the following technologies and tools is beneficial:

• React, Bootstrap, Tailwind, or another frontend framework
• Redis
• RabbitMQ
• Nginx
• Git
• A major cloud provider such as AWS, Google Cloud Platform, or Azure

What You Will Be Doing Daily Responsibilities

• Architect, build, maintain, and deploy new business features across the platform.
• Collaborate with product and engineering teams in a team-oriented development environment.
• Communicate directly with business stakeholders to understand requirements and translate them into technical solutions.
• Write and maintain data access logic using Dapper and MySQL.
• Optimize database queries and preserve or improve performance to meet established SLAs.
• Introduce and maintain automated unit and integration test coverage using NUnit as a standard part of feature development and service extraction.
• Analyze and refactor legacy modules within the existing platform into independently deployable and testable ASP.NET Core services.
• Follow the established platform decomposition roadmap while maintaining the reliability of the existing monolith.
• Define service contracts and communication patterns between newly extracted services and the remaining monolithic application during the transition.

The Opportunity

• Join an established fintech company building and maintaining its own core business platform.
• Contribute to new product functionality while helping modernize a large-scale application.
• Have meaningful involvement in backend architecture, service decomposition, database performance, and engineering quality.
• Help improve automated testing practices and establish maintainable development standards across the platform.