Mid-Senior Software Developer (.NET)

Colossus Technologies Group; Boston (MA); Hybrid; USD 120,000 - 170,000; Full time

Benefits offered by this job

Hybrid work option

Job summary

Colossus Technologies Group in Boston, MA, seeks a Senior Software Developer to build backend services, APIs, and data-processing pipelines using C#/.NET and SQL Server. You’ll contribute to scalable data solutions in a collaborative, Agile environment.

Focus areas include optimizing relational data models, troubleshooting production issues, and guiding best practices while partnering with product and engineering stakeholders to deliver reliable, high‑quality software.

Qualifications

• 5+ years of professional software development experience.
• Strong hands-on experience with C#, .NET / .NET Core, and object-oriented programming.
• Strong SQL Server experience, including complex queries, stored procedures, query tuning, indexing, and performance optimization.
• Experience developing REST APIs and integrating with internal or third‑party systems.
• Solid understanding of relational database design, normalization, and data integrity.
• Experience with Entity Framework, Dapper, or similar ORM/data‑access tools.
• Familiarity with Git‑based source control and CI/CD practices.
• Strong troubleshooting, communication, and collaboration skills.

Responsibilities

• Design, develop, test, and maintain backend applications using C# and the .NET framework / .NET Core.
• Build and support RESTful APIs, services, integrations, and data-processing workflows.
• Write, optimize, and troubleshoot complex SQL Server queries, stored procedures, functions, and database objects.
• Design and improve relational data models, schemas, and database performance.
• Investigate production issues, diagnose root causes, and deliver durable fixes.
• Participate in code reviews and contribute to engineering standards, documentation, and best practices.
• Collaborate with cross-functional teams in an Agile delivery environment.
• Help modernize legacy applications and improve reliability, scalability, and maintainability.

Skills

C# & .NET

SQL Server

REST APIs

Object-oriented programming

Agile development

Git

Tools

Entity Framework

Dapper

CI/CD

Git

Job description

Senior Software Developer — C#/.NET, SQL, & Data Focus

Experience: 5+ years

We’re seeking a Senior Software Developer to build and support data-driven applications in a collaborative engineering environment. This role is ideal for someone who combines strong backend .NET development skills with deep SQL Server and database expertise.

You’ll work on scalable APIs, business applications, integrations, and data solutions while partnering closely with product, engineering, and business stakeholders.

What you’ll do

• Design, develop, test, and maintain backend applications using C# and the .NET framework / .NET Core.
• Build and support RESTful APIs, services, integrations, and data-processing workflows.
• Write, optimize, and troubleshoot complex SQL Server queries, stored procedures, functions, and database objects.
• Design and improve relational data models, schemas, and database performance.
• Investigate production issues, diagnose root causes, and deliver durable fixes.
• Participate in code reviews and contribute to engineering standards, documentation, and best practices.
• Collaborate with cross-functional teams in an Agile delivery environment.
• Help modernize legacy applications and improve reliability, scalability, and maintainability.

What we’re looking for

• 5+ years of professional software development experience.
• Strong hands-on experience with C#, .NET / .NET Core, and object-oriented programming.
• Strong SQL Server experience, including complex queries, stored procedures, query tuning, indexing, and performance optimization.
• Experience developing REST APIs and integrating with internal or third‑party systems.
• Solid understanding of relational database design, normalization, and data integrity.
• Experience with Entity Framework, Dapper, or similar ORM/data‑access tools.
• Familiarity with Git‑based source control and CI/CD practices.
• Strong troubleshooting, communication, and collaboration skills.

Nice to have

• Experience with Azure, AWS, or cloud‑native application development.
• Exposure to SSIS, SSRS, Power BI, ETL pipelines, or other reporting/data‑platform tools.
• Familiarity with microservices, event‑driven architecture, or message queues.
• Experience working in regulated, financial, healthcare, insurance, or enterprise environments.

Why consider this role

• Hybrid flexibility in the Boston area.
• Opportunity to own meaningful backend and data‑focused engineering work.
• Collaborative team with exposure to modern application‑development and cloud practices.
• Strong opportunity to influence system design, performance, and technical direction.