Freelance Mobile App Developer (iOS / Android) at Mindrift · Madrid

Mindrift is looking for skilled Mobile App Developers (React Native, Flutter, Swift, or Kotlin) to join the Tendem project (https://tendem.ai/) and build native and cross-platform mobile applications for real-world use cases. In this role, you'll apply your mobile engineering expertise to build stable, performant, and user-friendly applications for iOS and Android. This part-time remote opportunity is ideal for professionals with hands-on experience shipping iOS and/or Android apps, working with platform APIs, and handling the full mobile development lifecycle.

What We Do

The Mindrift platform connects specialists with innovative technology projects. Our mission is to help develop high-quality AI technologies by combining real-world expertise from professionals across the globe with advanced AI development efforts.

About the Role

This is a freelance role for a Tendem project. As a Mobile App Developer, you'll design, build, and refine mobile applications across categories such as utilities, fitness/wellness, games, productivity, delivery, and content apps — for iOS, Android, or both, using native or cross-platform frameworks.

Key Responsibilities

• Build mobile applications using React Native, Flutter, Swift (iOS), or Kotlin (Android).
• Implement responsive mobile UIs that follow platform conventions (iOS HIG, Material Design).
• Integrate native device features (camera, push notifications, location, storage, biometrics).
• Connect apps to backend APIs, handle offline state, caching, and synchronization.
• Implement monetization features where required (in-app purchases, ads, subscriptions).
• Review, debug, optimize, and refactor mobile application code to improve correctness, performance, battery efficiency, and maintainability.
• Debug platform-specific issues and prepare builds for distribution (TestFlight, Play Console).

Educational qualifications

• At least 3 years of relevant experience in mobile app development (required).
• Bachelor's or Master's Degree in Computer Science, Engineering, Information Technology, or related technical fields is a plus.

Academic and/or Professional Experience

Candidates should have a strong foundation in mobile application development, platform-specific UI/UX patterns, and building stable, high-quality mobile experiences for iOS and Android. We are looking for specialists who can confidently work with native or cross-platform frameworks, integrate device APIs and backend services, and build production-ready mobile applications. Strong attention to detail, performance awareness, and the ability to work independently are essential.

Technical Skills (Essential)

• Hands-on experience with at least one of: React Native, Flutter, Swift/SwiftUI (iOS), or Kotlin/Jetpack Compose (Android).
• Solid understanding of mobile UI patterns, navigation, state management, and platform guidelines.
• Experience integrating REST APIs, handling async data, and managing local storage.
• Familiarity with native device APIs (notifications, camera, location, storage, biometrics).
• Experience with mobile build tools, code signing, and submission to App Store / Google Play.
• Experience implementing in-app purchases, ads, or subscriptions is a plus.
• Familiarity with backend services such as Firebase, Supabase, or similar is a plus.

Additional requirements

• Strong attention to detail and commitment to performance, stability, and platform polish.
• Self-directed work ethic with the ability to ship complete mobile features independently.
• Portfolio of shipped mobile apps (required, with App Store / Google Play links preferred).
• English proficiency: Upper-intermediate (B2) or above (required)

Project time expectations

For this project, tasks are estimated to require around 10–20 hours per week during active phases, based on project requirements. This is an estimate, not a guaranteed workload, and applies only while the project is active.

Compensation

On this project, contributors can earn up to $50 per hour equivalent, depending on their level and pace of contribution.

Compensation varies across projects depending on scope, complexity, and required expertise. Please note that other projects on the platform may offer different earning levels based on their requirements.

Why this freelance opportunity might be a great fit for you?

• Work fully remote on your own schedule with just a laptop and stable internet connection.
• Apply your expertise to real-world technology projects while gaining experience building high-quality solutions for a global platform.
• Participate in performance-based bonus programs that reward high-quality work and consistent delivery.