Senior Software Engineer .NET
Remote
Colombia
We are seeking a highly skilled Senior .NET Developer to take ownership of maintaining, optimizing, and modernizing legacy .NET Framework and ASP.NET WebForms applications. This role involves tackling complex technical challenges, collaborating with cross-functional teams, and driving modernization initiatives toward .NET Core and modern web architectures. The ideal candidate combines strong backend expertise with solid frontend integration skills and a proactive, leadership-oriented mindset.
Requirements
- 5+ years of experience with .NET Framework (3.5–4.8). Expert knowledge of ASP.NET WebForms (server controls, view state, event-driven model) and deep understanding of its limitations.
- Strong skills in C#, VB.NET (if applicable), ADO.NET, and Entity Framework.
- Advanced knowledge of HTML, CSS, JavaScript, and jQuery integration within WebForms.
- Hands-on experience configuring IIS for performance and scaling.
- Strong database expertise (query optimization, schema design, performance tuning).
- Experience with Visual Studio and advanced usage of Git/TFS or similar
- Ability to work independently on complex tasks and provide technical leadership.
- Excellent communication skills with both technical and non-technical stakeholders.
Nice to Have
- Proven experience migrating legacy apps to modern .NET (Core/6/7/8) and ASP.NET MVC / Razor Pages / Blazor
- Knowledge of migration strategies from WebForms to modern frameworks
- Familiarity with cloud deployment in Azure/AWS. Experience designing and integrating REST APIs.
Responsibilities
- Lead maintenance and optimization of legacy .NET Framework and ASP.NET WebForms applications. Investigate and resolve complex production issues, ensuring system stability.
- Communicate directly with business analysts and stakeholders to define solutions.
- Set coding standards, conduct code reviews, and mentor team members.
- Design and execute large-scale refactoring and modernization strategies.
- Plan and drive system upgrades or migrations to .NET Core/.NET 6+.
- Ensure application security, scalability, and performance.
- Work with SQL Server and other databases, including optimization of large-scale queries.
- Collaborate closely with QA, DevOps, and client teams to improve delivery processes.
We offer:
Well-being:
- 10 working days of Paid Day Off within an individual year.
- Up to 15 working days of Unpaid days off within an individual year.
Professional Growth:
- Sombra University courses – enjoy a range of learning opportunities through Sombra University. It offers many educational courses, as well as educational lectures on a variety of topics.
- Sombra Around Tech – community attendance – Sombra unites engineers and experts in several areas: Front-end, Back-end, QA, DevOps, and Вusiness Analysis.
- Mentorship program – available on request.
- UDEMY online course platform – stay up-to-date with the latest technologies and programming languages.
- English courses and Speaking Club – attend English classes twice a week in small groups.
Added advantages:
- Work equipment (Laptop, monitor, and small devices compensation).
- Sombra’s referral program.
- If you know someone you believe is a good fit for our cooperation, you can recommend them and get a reward.
- Public Holidays – celebrate 18 statutory holidays in Colombia.
- Sombra events – Join Sombra’s traditional events (both online and offline).
