Senior Software Developer

Join It; Greater London; On-site; GBP 70,000 - 90,000; Full time

Benefits offered by this job

Competitive pay

Professional growth opportunities

Collaborative team environment

High ownership and influence on product direction

Job summary

A fast-growing software company in London is seeking a Senior Software Developer to enhance their B2B SaaS platform. This role involves owning problems end-to-end, designing and shipping features, and maintaining high code quality. The ideal candidate has over 7 years of software development experience, excels in building production SaaS applications, and is skilled in backend languages and API design. This opportunity offers competitive pay and a chance to influence product development in a collaborative environment.

Qualifications

• 7+ years professional software development experience.
• Strong experience building and maintaining production B2B SaaS applications.
• Deep proficiency in at least one modern backend language or framework.
• Strong understanding of relational databases, data modelling, and migrations.
• Experience designing and consuming APIs.
• Comfortable working across the stack (frontend, backend, integrations).
• Experience working in lean teams with high ownership and autonomy.
• Strong communication skills and a product-oriented mindset.

Responsibilities

• Design, build, and ship high-quality product features.
• Take ownership of key parts of the codebase.
• Write clean, well-tested, and maintainable code.
• Improve application performance and reliability.
• Investigate and resolve complex bugs and production issues.
• Support and mentor other engineers through code reviews.

Skills

Software development

B2B SaaS applications

API design

Application security

Data modeling

Mentorship

Job description

Join It is a fast-growing B2B SaaS company helping organisations manage and grow their memberships. We support thousands of associations, clubs, and communities globally with software that simplifies recurring billing, member engagement, and day-to-day operations.

We’re a lean, ambitious team with big growth goals, and we’re looking for an exceptional Senior Software Developer to help scale our platform, ship meaningful product improvements, and raise the bar on engineering quality.

This role is for a senior, hands-on engineer who enjoys owning problems end-to-end - from understanding customer needs through to designing, building, and shipping robust solutions in production.

You’ll work closely with Product, Leadership, and other Engineers, take real ownership of core systems, and play a key role in shaping how we build and scale Join It.

Responsibilities

• Product-Focused Development: Design, build, and ship high-quality product features that directly support customer needs and business growth.
• System Design & Technical Ownership: Take ownership of key parts of the codebase and contribute to system design decisions that balance scalability, performance, and maintainability.
• Code Quality & Best Practices: Write clean, well-tested, and maintainable code; help set and uphold engineering standards and best practices.
• Performance, Reliability & Scale: Improve application performance, reliability, and resilience as the platform scales in usage, data volume, and customer complexity.
• Collaboration & Delivery: Work closely with Product and Design to break down problems, shape solutions, and deliver iteratively without unnecessary process.
• Technical Problem Solving: Investigate and resolve complex bugs, edge cases, and production issues with a strong focus on customer impact.
• Mentorship & Team Contribution: Support and mentor other engineers through code reviews, pairing, and knowledge sharing, helping raise the overall engineering bar.
• Continuous Improvement: Proactively identify technical debt, architectural improvements, and tooling enhancements that improve developer velocity and product quality.
• AI-Enabled Development: Leverage AI tools and workflows (e.g. coding assistants, testing, debugging, prototyping, documentation) to improve development speed, code quality, and problem-solving - and help the team adopt effective AI-assisted practices where valuable.

Qualifications

• 7+ years professional software development experience
• Strong experience building and maintaining production B2B SaaS applications
• Deep proficiency in at least one modern backend language or framework
• Strong understanding of relational databases, data modelling, and migrations
• Experience designing and consuming APIs
• Strong grasp of application security, performance, and reliability best practices
• Comfortable working across the stack (frontend, backend, integrations) as needed
• Experience working in lean teams with high ownership and autonomy
• Strong communication skills and a product-oriented mindset
• Experience using AI tools to support software development (e.g. code generation, refactoring, testing, or prototyping) in a production environment
• Curiosity and pragmatism around applying AI where it meaningfully improves developer productivity or product capabilities

Nice to have (but not required)

• Experience with payments, subscriptions, or billing systems
• Experience working with third-party integrations and APIs
• Experience in a scale-up or high-growth SaaS environment
• Familiarity with cloud infrastructure and modern deployment pipelines
• Competitive pay.
• Opportunity to work with a fast growing SaaS platform.
• High ownership and meaningful influence on product and technical direction
• Collaborative, supportive, low-bureaucracy team environment
• Strong opportunity for professional growth as the platform and team scale

We are an equal opportunity employer and value diversity at our company. We do not discriminate on the basis of race, religion, color, national origin, gender, sexual orientation, age, marital status, veteran status, or disability status.