Full Stack Senior Developer For SAAS DFY Startup, Long Term

Full-Stack Developer for Long-Term SaaS Platform I’m looking for a highly skilled and dependable full-stack developer to work with me long-term on KS OS, a growing web-based business operating system. This is not a one-off website project. I’m looking for someone who can understand an existing codebase, solve problems independently, improve the platform over time, and become a trusted technical partner. I am looking to build a long-term working relationship with a developer who communicates clearly, works reliably, and is comfortable working across the full stack. About KS OS KS OS is a modular platform designed to help businesses manage areas such as: Customers and contacts Projects and tasks Documents and reports Business operations Automations and integrations User accounts, permissions and dashboards AI-powered features The platform already has an existing codebase, development environment and deployment process. You will initially work on improving and expanding the current system rather than starting everything from scratch. Technical Skills You should have strong practical experience with: React and Next.js TypeScript Node.js and API development PostgreSQL and database design Git and GitHub workflows REST APIs and third-party integrations Authentication and role-based permissions Responsive frontend development Debugging existing production applications Linux servers, VPS deployments and system services Cloudflare, DNS and web security fundamentals Experience with Supabase, Prisma, Tailwind CSS, Vercel, AI APIs or SaaS platforms would be an advantage. Deployment Environment KS OS uses both: VPS deployment for the main API and backend services Cloudflare deployment/services where appropriate You should be comfortable identifying whether a change requires a VPS deployment, a Cloudflare deployment, or both. What You Will Do Your responsibilities may include: Understanding and maintaining the existing KS OS codebase Building new features from written requirements and designs Fixing frontend, backend and database issues Creating secure and reliable APIs Improving application speed, accessibility and usability Reviewing and improving existing code Writing database migrations when required Testing changes before deployment Deploying updates safely to staging and production Documenting important technical decisions Communicating blockers and risks early Suggesting better technical solutions when appropriate Who I’m Looking For The right developer will be: Highly skilled and technically confident Honest about what they know and do not know Able to investigate problems independently Comfortable working with an existing codebase Reliable with deadlines and communication Interested in a stable, long-term opportunity Careful when making production changes Able to explain technical decisions clearly Focused on clean, maintainable and secure code I do not want someone who simply copies AI-generated code without understanding it. AI development tools can be used, but you must review, test and take responsibility for everything you submit. Working Relationship This will begin with a small paid trial task. If the trial goes well, there will be regular ongoing work. I am looking for good value and a sustainable long-term rate. I understand that strong developers deserve fair compensation, but I am not looking for expensive agency pricing. The workload may initially be part-time and increase as the platform grows. Communication We will mainly communicate through Upwork and project-management tools. You must be able to read and write technical English confidently. You should provide clear updates covering: What you completed What files or systems you changed Whether the change affects the VPS, Cloudflare, or both What you tested Any risks, blockers or follow-up work Application Questions Please begin your proposal with the words “KS OS Developer” so I know you have read the complete description. Generic or automated proposals that do not answer the questions will not be considered. Paid Trial The shortlisted candidate will receive a small paid technical task involving the existing KS OS codebase. The trial will assess: Code quality Problem-solving ability Communication Git discipline Testing Security awareness Ability to follow deployment instructions Ability to distinguish between VPS and Cloudflare deployment requirements The goal is to find one reliable developer who can grow with the platform over the long term.