Senior Software Developer

*Strictly no recruitment agencies

Full time Senior Software Developer wanted.

Calling All Senior Software Developers!

Ready to make a real impact?

We're on the lookout for a Senior Software Developer to join our dynamic team.

If you're passionate about coding and eager to tackle exciting challenges, this is the opportunity for you. As a Senior Software Developer, you'll lead the charge on our most innovative product development, collaborating with a talented team to bring game-changing ideas to life.

Forget the corporate jargon – we're all about getting things done and making a difference. If you're ready to roll up your sleeves, we want to hear from you. Let's build the future together.

TellJO is a for-profit, mission-driven company proactively supporting people susceptible to vulnerability. TellJO puts purpose before profit and believes in a fair and equal society for all.

Working for a startup is not easy. TellJO is seeking an individual who wants to have a tangible impact on our business and has the courage and determination to drive the product development forward at pace.

Role and Responsibilities

Your Role in Our Mission

As a Senior Software Engineer at TellJO, you’ll lead the design and delivery of robust, secure, and scalable technology that directly improves people’s lives.

This is more than coding — you’ll:

• Architect and build complex, maintainable systems using C#, .NET, and React (ASP.NET is a plus).
• Set technical standards for clean, testable, and efficient code, using nUnit, Moq, and modern CI/CD pipelines (Azure DevOps).
• Own deployment pipelines, ensuring secure, reliable, and timely releases to Azure.
• Champion security best practices, performance optimizations, and database efficiency — from query tuning to thread management.
• Drive technical excellence, providing mentorship, conducting code reviews, and guiding team members on best practices and modern patterns.
• Collaborate with stakeholders to shape the roadmap, break down complex problems, and deliver high-impact solutions.
• TellJO is an office working environment, working from Lancing, near Worthing

What you bring

You’re an experienced engineer ready to step up, lead by example, and drive meaningful change. You have:

• Extensive experience building full-stack applications, with a strong focus on front-end (React, TypeScript) and modern C# (.NET Core preferred).
• Proven ability to architect, refactor, and migrate legacy solutions (.NET 4.8 experience a plus).
• Solid grounding in unit testing, mocking, CI/CD, and cloud deployments (Azure).
• Deep knowledge of security principles, scalability, and performance tuning in production environments.
• Strong analytical and problem-solving skills — you tackle complex challenges with a pragmatic mindset.
• A passion for mentorship and technical leadership, with experience guiding less-experienced engineers to success.
• A collaborative, proactive attitude — you thrive in cross-functional teams where your expertise shapes products that matter.
• Proficiency and experience using modern LLMs to assist with software development.
• Experience with Entity Framework Core ORM or similar, against MS SQL Server or similar RDBMS**,** is essential.

Experience with Wordpress is a bonus.

Additional Notes

Why TellJO?

• Purpose-Driven Work – Help vulnerable people avoid crisis and regain control
• Innovative Tech – Work on meaningful, modern software that makes a difference
• Growth & Learning – Be part of a team that supports continuous development

Proven Results – Be proud of the measurable social impact you help create

Office Based - Worthing (Brooklands House - Lancing)

37 Hours per week Monday to Friday 28 days holiday including bank holidays (per annum) (pro rata)

Job Type: Full Time

Salary: £45,000 to £57,000 per annum

Other: The job is office based in Worthing, so ability to commute daily is essential

For an informal chat reach out to [email protected] 07901 555230

Job Type: Full-time

Pay: £45,000.00-£57,000.00 per year

Work Location: In person