Mobile Application Developer (Kotlin Multiplatform)

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., * Design, develop, and maintain mobile applications using Kotlin Multiplatform and Compose Multiplatform

• Apply object-oriented programming principles and modern mobile architecture patterns
• Integrate mobile clients with Django backend APIs, including FHIR R4 clinical interoperability endpoints
• Contribute to web application development that supports mobile workflows
• Participate in wearable device integration (BLE, embedded data pipelines) as that programme matures
• Troubleshoot, debug, and optimise applications for performance and reliability
• Collaborate with cross-functional teams across engineering, clinical, research, and regulatory domains
• Participate in code review, architectural decisions, and continuous improvement of our delivery practices

Must have

• Proficiency in mobile application development, with hands-on experience in Kotlin Multiplatform and Compose Multiplatform in production or near-production environments
• iOS development experience (required, for platform-specific KMP work)
• Strong command of object-oriented programming and clean architecture patterns
• Working knowledge of Python (you will on occasion read and write Django code)
• Experience with Git and modern version control workflows
• Strong problem-solving and analytical skills
• Excellent written and verbal communication
• UK 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 have

• Bachelor's degree in Computer Science, Software Engineering, or a related field
• JavaScript experience (our cognitive task codebase is substantial)
• Experience in regulated environments: healthcare, medical devices, social care
• Familiarity with FHIR, SAML, or enterprise SSO
• Experience with wearable devices, BLE, or embedded sensor integration
• Cloud-based infrastructure experience (AWS preferred)
• Exposure to agile delivery practices

Full Stack:

• Mobile: Kotlin Multiplatform, Compose Multiplatform
• Backend: Django, Python, Postgres, Redis
• Infrastructure: AWS (ECS, CloudFront, RDS), Terraform
• Web frontend: Django SSR with HTMX
• Interoperability: FHIR R4, SAML 2.0, Keycloak

• 12-month fixed-term contract with strong likelihood of extension
• Hybrid working from our London office
• Flexitime, Monday to Friday
• Company pension
• Employee discount scheme
• Work-from-home equipment for home days
• Competitive salary, discussed at first interview based on experience
• Immediate start available

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.