Full Stack Developer

UnknwnAI is looking for a Mid-Level Full Stack Developer to join our growing engineering team.We develop modern software across SaaS, enterprise systems, healthcare technology, AI, integrations and business-critical applications. We work across a broad technology landscape, so we are looking for a developer with strong full-stack fundamentals who is comfortable working beyond a single framework or language.This role is suited to someone with approximately 3+ years of professional software development experience who can contribute across frontend, backend, databases, APIs and integrations, while continuing to broaden their technical capabilities.You should be comfortable taking a requirement or problem, understanding the wider context, designing an appropriate solution and seeing it through to a reliable production implementation.What you will be doing: Designing, developing and maintaining full-stack applicationsBuilding modern frontend applications and user interfacesDeveloping backend services, APIs and business logicDesigning and working with relational databasesWriting efficient SQL queries and working with complex dataBuilding integrations with third-party services, platforms and APIsWorking across new applications as well as established production systemsTaking features from initial requirements through development, testing and deploymentInvestigating application, API, database and infrastructure issuesDebugging problems across multiple layers of a system rather than treating symptoms in isolationContributing to application architecture and technical design decisionsImproving performance, scalability, maintainability and reliabilityImplementing appropriate authentication, authorization and security controlsWorking with cloud-hosted applications and servicesParticipating in code reviews and helping maintain engineering standardsWriting clear, maintainable and reusable codeWorking collaboratively with developers and other members of the businessContributing ideas and proposing better technical approaches where appropriateLearning and working with unfamiliar technologies where a project requires themEssential: Around 3+ years of professional software development experienceStrong understanding of full-stack software developmentGood experience building modern web applicationsStrong programming fundamentals and understanding of software design principlesCommercial experience with at least one modern frontend framework such as React, Next.js, Vue or AngularExperience developing backend applications, APIs or servicesExperience with backend technologies such as Node.js, TypeScript/JavaScript, C#/.NET, Python, Java or similarStrong understanding of REST APIs and application integrationsGood knowledge of SQL and relational databasesExperience with databases such as PostgreSQL, SQL Server, MySQL or similarUnderstanding of data modelling and relational database designGood knowledge of HTML, CSS and modern frontend developmentExperience using Git within a collaborative development environmentUnderstanding of authentication, authorization and common web security principlesAbility to debug problems across frontend, backend, API and database layersAbility to understand and work confidently within existing codebasesAbility to translate business requirements into practical technical solutionsGood understanding of application architecture and separation of concernsStrong problem-solving skillsGood attention to detail and a disciplined approach to testing your own workClear written and verbal communicationAbility to work independently while remaining closely connected with the wider teamAvailability to work standard UK business hoursOur Current Technology Landscape:Our technology varies between products and projects and will continue to evolve.Technologies we currently work with include:TypeScriptJavaScriptNext.jsReactNode.jsTailwind CSSPostgreSQLMicrosoft SQL ServerPythonC# / .NETREST APIsAWSMicrosoft AzureDockerGitHubExperience with every technology above is not required.We are more interested in developers who have strong engineering fundamentals and can confidently move between technologies than someone whose experience is limited to one specific framework.Useful Additional Experience:Experience in any of the following would be beneficial:AWS or Microsoft AzureCloud application architectureDocker and containerized environmentsCI/CD pipelinesAutomated testingRedis or other caching technologiesRabbitMQ, message queues or event-driven systemsBackground jobs and asynchronous processingMicroservices or distributed systemsSaaS and multi-tenant application architectureThird-party API integrationsE-commerce or marketplace integrationsERP or complex business management systemsHealthcare technologyAI and LLM integrationsAuthentication and identity platformsPerformance optimizationApplication monitoring and loggingLegacy system integration or modernizationSecure software developmentHigh-availability or business-critical systemsWhat we expect from our Developer:OwnershipYou should be comfortable taking responsibility for a piece of work from beginning to end.That includes understanding the problem, identifying dependencies, considering edge cases, implementing the solution, testing it properly and making sure the finished result actually meets the requirement.Problem SolvingSoftware development frequently involves unfamiliar problems.We expect developers to investigate issues properly, read documentation, understand existing code, test assumptions and work methodically towards the root cause.Knowing everything is not expected.Being capable of finding things out is.Engineering JudgementThere is rarely only one way to build something.We value developers who can consider maintainability, performance, security, complexity and delivery time before choosing an approach.We also want people who are comfortable questioning an existing approach when they can explain why another solution would be better.CommunicationOur team works remotely, so communication is important.We expect developers to:Raise blockers earlyAsk questions when requirements genuinely need clarificationCommunicate progress clearlyExplain technical decisionsFlag potential risks before they become problemsWork collaboratively rather than disappearing into tasksQualitySpeed matters, but not at the expense of reliability.Developers should care about:Clean and maintainable codeAppropriate testingError handlingSecurityPerformanceEdge casesData integrityThe wider impact of changes to a systemAdaptabilityWe do not want developers whose capability begins and ends with one framework.Technology changes, projects have different requirements and sometimes the correct solution involves working in an unfamiliar part of the stack.You should be willing and able to learn.Why Join UnknwnAI?Work across a broad range of technically challenging softwareBuild both new applications and major functionality for established systemsGain exposure across frontend, backend, APIs, databases, integrations and cloud infrastructureWork with different technologies rather than being restricted to a single frameworkHave meaningful input into technical decisionsTake genuine ownership of features and systemsWork directly with a growing engineering team without unnecessary layers of managementDevelop experience across SaaS, enterprise software, healthcare technology, AI and complex business systemsJoin a growing company where your responsibilities and technical scope can expand significantly over timeHow to Apply:Please submit your CV along with your GitHub profile, portfolio or examples of relevant technical work, where available.During the interview process, we will focus on what you personally contributed to previous projects, how you approach technical problems and how well you understand the systems you have worked on.We are less interested in how many technologies appear on your CV but more interested on whether you can demonstrate strong engineering fundamentals, genuine hands-on experience and the ability to learn and solve problems effectively.