Mobile Application Developer (Kotlin Multiplatform)H2 Cognitive Designs | London, Hybrid | Full-time | 12-month FTC (likely extension) | Immediate startCompany Description:H2 Cognitive Designs (H2CD) develops cognitive testing and remote clinical assessment tools for healthcare providers, academic institutions, and defence and research partners. Our flagship platform, Cognitron, is used across the NHS, UK and allied defence programmes, and international research programmes, and is the designated cognitive outcome platform for TBI-REPORTER, the UK's NIHR-backed traumatic brain injury research infrastructure. You may recognise our work from BBC2 Horizon's Great British Intelligence Test (370,000+ participants).Cognitron Health is progressing through FDA 510(k) submission, and we hold one of the world's largest normative cognitive datasets, enabling benchmarking across a wide range of mental health and neurological conditions.Our mission is to build innovative, high-quality tools that measurably improve cognitive and clinical assessment at scale.Role Description:This is a full-time hybrid role based in Greater London, with a mix of office and home days. You will design, develop, and maintain our mobile applications for iOS and Android using Kotlin Multiplatform (KMP) and Compose Multiplatform, directly contributing to the scalability, performance, and clinical utility of our flagship products.You will also work on our web backend (Python, Django, Postgres) where it intersects with mobile workflows, and contribute to forthcoming wearable device integration for passive cognitive and physiological data collection.Key responsibilities:Design, develop, and maintain mobile applications using Kotlin Multiplatform and Compose MultiplatformApply object-oriented programming principles and modern mobile architecture patternsIntegrate mobile clients with Django backend APIs, including FHIR R4 clinical interoperability endpointsContribute to web application development that supports mobile workflowsParticipate in wearable device integration (BLE, embedded data pipelines) as that programme maturesTroubleshoot, debug, and optimise applications for performance and reliabilityCollaborate with cross-functional teams across engineering, clinical, research, and regulatory domainsParticipate in code review, architectural decisions, and continuous improvement of our delivery practicesQualifications:Must haveProficiency in mobile application development, with hands-on experience in Kotlin Multiplatform and Compose Multiplatform in production or near-production environmentsiOS development experience (required, for platform-specific KMP work)Strong command of object-oriented programming and clean architecture patternsWorking knowledge of Python (you will on occasion read and write Django code)Experience with Git and modern version control workflowsStrong problem-solving and analytical skillsExcellent written and verbal communicationUK right to work (non-negotiable, due to client sensitivity and regulatory requirements)Able to attend our London office on required days (hybrid working)Nice to haveBachelor's degree in Computer Science, Software Engineering, or a related fieldJavaScript experience (our cognitive task codebase is substantial)Experience in regulated environments: healthcare, medical devices, social careFamiliarity with FHIR, SAML, or enterprise SSOExperience with wearable devices, BLE, or embedded sensor integrationCloud-based infrastructure experience (AWS preferred)Exposure to agile delivery practicesFull Stack:Mobile: Kotlin Multiplatform, Compose MultiplatformBackend: Django, Python, Postgres, RedisInfrastructure: AWS (ECS, CloudFront, RDS), TerraformWeb frontend: Django SSR with HTMXInteroperability: FHIR R4, SAML 2.0, KeycloakWhat we offer:12-month fixed-term contract with strong likelihood of extensionHybrid working from our London officeFlexitime, Monday to FridayCompany pensionEmployee discount schemeWork-from-home equipment for home daysCompetitive salary, discussed at first interview based on experienceImmediate start availableHow to applyApply directly through LinkedIn with your CV and a short note on your Kotlin Multiplatform experience. Links to relevant projects, GitHub, or technical writing are welcome and will accelerate your application.We review every application and respond quickly to strong candidates.H2 Cognitive Designs is an equal opportunity employer. We are committed to building a team that reflects a broad range of backgrounds, perspectives, and experiences.