(IT solutions) Senior Android Developer JR296, JR295

Rebtel Networks AB

What will you do? As a Senior Android Engineer at Rebtel, you will be part of our Frontend team, helping modernize and evolve the Rebtel Android app. We are in the middle of migrating from Java to Kotlin and Jetpack Compose while continuously shipping product features to a global user base. You’ll work in a small, empowered team where your technical decisions matter. This role is a mix of building new features, refactoring legacy code, collaborating cross-functionally, and shaping the future of our Android platform. Areas of ownership: Drive the migration from Java to a modern Kotlin + Compose stack Refactor code that slows us down and proactively pay down tech debt Build and modernize Android features using Kotlin and Jetpack Compose Contribute to architecture decisions (MVVM/MVI, Coroutines, platform improvements) Collaborate closely with iOS, Web, Product, Design, and QA to ship the right solutions Improve tooling, testing practices, and CI/CD where needed Maintain and improve the overall health of the Android platform Requirements: You are an excellent communicator and collaborator. We work in English, but you will hear many languages in our Stockholm office 5+ years of experience building Android applications Strong knowledge of Kotlin (and solid Java understanding) Experience with modern Android architecture (Jetpack Compose, Coroutines, MVVM/MVI) Proven ability to work independently and ship high-quality code You are an excellent communicator and collaborator. We work in English, but you will hear many languages in our Stockholm office You care about the code you leave behind — you ship features without cutting corners You prefer simple, pragmatic solutions over clever complexity Experience migrating legacy Android codebases to modern stacks Experience with mobile CI/CD, testing, or DevOps practices is a plus It's a plus with experience with collaborating across platforms (iOS/Web) Why Rebtel? When you join Rebtel, you become part of a global team, bringing together diverse minds from every corner of the world. Our headquarter is nestled in Stockholm and here we strike a balance between dedicated work and more relaxed activities. Every Friday the unmistakable aroma of freshly popped popcorn fills the air, but our celebrations encompass everything from minor and major common accomplishments to cinnamon bun day. At Rebtel, you are the most important asset and we strive to provide a comprehensive package of benefits and perks that enhance your well-being and work experience. Here are some of the things you can expect from us: Pension Plan Health Checkups, Influenza shots and Private Medical Insurance Dental Insurance Occupational insurance Wellness allowance (5,000 SEK) Discount on gym memberships Bonus program Extra parental pay 30 days annual vacation Monday breakfasts Relocation Support, if you're joining us from afar, we'll assist you in making a smooth transition. Rebtel is an international workplace, and at the office, we speak English; therefore, high English proficiency is required. We are committed to being an LGBTQIA+ safe workplace, a place where individuals can be open about who they are without fear of discrimination or harassment. We are Rebtel. We come from all around the world to create products for anyone who has crossed a border. We believe in equal opportunity and value diversity at our company. We do not discriminate on the basis of race, religion, color, national origin, gender, sexual orientation, age, marital status, veteran status, or disability status.

Proton

Join Proton and build a better internet where privacy is the default Proton was founded in 2014 by scientists from CERN on a simple truth: privacy is a fundamental human right. Since then, we’ve built the world’s largest encrypted email service (Proton Mail) and expanded into Proton VPN, Proton Drive, Proton Pass, and Proton Calendar—tools used by millions globally to protect their freedom, fight censorship, and keep their data safe. In some situations, Proton has literally helped save lives! We are profitable, independent (no VC control), and selectively hire from the top ~1% of applicants. Our 500+ team members across 50+ countries come from leading organizations and elite academic backgrounds. We move fast, keep hierarchy light, and prioritize impact over optics. If you want to do meaningful work with exceptionally high-caliber people, this is it. Join us and do work you can truly be proud of. Check our open-source projects here! About Photos Join the team building Proton Drive Photos, a private photo storage designed so your memories belong only to you. We’re creating the encrypted alternative to Big Tech photo platforms, combining consumer-grade UX with uncompromising privacy. If you want to build products used by millions while helping fix the internet, we’d love to meet you. Role overview As a fullstack cross-platform Android Engineer, you'll play a pivotal role in developing Proton Photos using Jetpack Compose and Rust. You’ll use an end-to-end ownership approach, ensuring timely delivery of high-quality, scalable solutions that will delight our customers.  Key responsibilities * Develop and maintain cross-platform mobile applications for Android using a blend of cross-platform (Rust) and native technologies (Kotlin) * Take end-to-end ownership of mobile application development projects: you'll be comfortable with scoping projects, walking back from deadlines and being able to discern the important from the superfluous * Foster a culture of innovation by exploring new technologies, methodologies and approaches to mobile development – we tackle complex engineering challenges with creativity and ingenuity * Optimise mobile applications for performance, usability and responsiveness across different devices and screen sizes * Master memory management, multithreading and concurrency mechanisms to enhance performance and responsiveness of mobile applications * Design for scalability, considering factors such as data caching, network bandwidth and server load * Prioritise customer satisfaction by maintaining a customer-centric mindset throughout the development process, continuously seeking feedback and iterating to improve the user experience The ideal candidate will bring * Bachelor's degree in Computer Science, Engineering or related field (or equivalent work experience) * Excellent problem-solving skills and the ability to think outside the box to overcome challenges * Passion for continuous learning and driving change in the rapidly evolving field of mobile development * Excellent communication and interpersonal skills * Proven experience developing mobile applications for Android using Kotlin * Proficiency with Jetpack Compose for Android, and familiarity with Rust * Strong understanding of mobile app architecture, design patterns and best practices * Knowledge of memory management techniques and best practices * Experience with multithreading and concurrency in mobile applications * Good understanding of scalability considerations when it comes to engineering mobile applications * Previous experience working in a fast-paced, scale-up environment Even if you don’t meet all the requirements listed above but feel you could still be a great fit, please do apply. What we offer * Technology: we provide all the devices and software you need to excel in your role, ensuring you have the best tools at your disposal to achieve your goals * Learning & Development: we are committed to your professional growth – Proton offers various learning opportunities, including training programs, conferences/events and continual learning * Employee Benefits: comprehensive health insurance plans, competitive retirement savings options, generous vacation/leave policies and wellness programs * Stock Options: at Proton, we are all owners of the company and you get stock options when you join us * In-Person Collaboration: collaboration is easier and more effective in person, which is why we have offices in Geneva, Zurich, Prague, Barcelona, Paris, London, Vilnius, Skopje and Taipei – you can enjoy working from home for up to 30% of the time, while enjoying great company culture during our three core days in the office * Food: lunch and snacks are provided by Proton every day at our offices * Transport: we'll always support our employees with transport costs through subsidising public transport, bike allowances or parking spaces based on your office location * Flexible Working: you can define your own working hours as long as it works with team meetings * Work that Matters: Proton is a community-first organisation, started with the support of a crowdfunding campaign and built with community input – to this day, Proton’s only source of revenue is user subscriptions: over 100 million people trust and support Proton, and we put our users and community first in everything we do (read more about our impact here) Our commitment to diversity and inclusion At Proton, we believe diversity drives innovation and strengthens our mission to provide privacy as a default for all. We are committed to fostering an inclusive environment where all individuals, regardless of race, ethnicity, gender, age, sexual orientation, physical ability or socio-economic background feel valued and empowered. We strive to create equal opportunities, promote open dialogue and support continuous learning to ensure every voice is heard and respected. If you need any extra support or reasonable adjustments during the hiring process, please let your talent partner know. Candidate privacy notice When you apply for a position, refer a candidate or are considered for a role at Proton Technologies AG (Proton, we, us or our), your information is stored in Greenhouse, in accordance with its Service Privacy Policy. This information is used to evaluate your suitability for the posted position. We also retain this information for consideration for future roles that you may apply for or that we believe may align with your background and skills. If we no longer have a legitimate business need to process your information, we will either delete or anonymise it. Should you have any inquiries about how we use or manage your information or if you wish to access, correct or delete your data, please contact our privacy team at careers@proton.ch. Proton does not accept unsolicited CVs from any sources other than directly from candidates. We will not pay a fee for any placement resulting from an unsolicited offer, even if the candidate is subsequently hired by Proton. To learn more about our privacy policy, please visit our privacy policy page. #LI-ONSITE

Sumup

Salary range: 18 850 - 29 660 PLN per month About the team SumUp’s Point-of-Sale (POS) solution empowers cafes, shops, bars, hair salons, and other businesses to operate efficiently and grow. It offers a wide range of features, including product catalogs, inventory management, business analytics, compliance support, and loyalty tools. Our POS solution integrates seamlessly into the SumUp SuperApp, which supports both our proprietary register hardware and mobile devices like tablets and phones. As a Senior Android Developer, you’ll collaborate with a dynamic, cross-functional team of Product Managers, Product Designers, Engineering Managers, and fellow engineers. About the role We’re evolving toward a Kotlin Multiplatform (KMP) strategy, enabling shared development across Android and iOS. In this role, you’ll learn, refine, and help implement this technology, shaping the future of our mobile apps. You’re a developer who values user-centric design, precision, and seamless collaboration. You bring structure to communication and thrive in a cross-functional environment.  This role will be a B2B based role in Warsaw. What you’ll do * Build new features for the item catalog within the SumUp SuperApp * Help improve the architecture of the application and contribute to our Kotlin Multiplatform strategy * Enhance and maintain our unified android app, distributed across 60+ countries, ensuring high-quality, scalable solutions * Shape the product’s evolution by identifying opportunities for improvement and contributing to daily decision-making * Write thorough documentation and implement robust testing for features before shipping * Collaborate closely with Designer, Product Manager and Android engineers to deliver a unified UX experience across platforms You’ll thrive in this role if: * You have 8+ years experience in mobile engineering with Android and Kotlin. * You have 2+ years of experience working with Jetpack Compose. * You have a solid understanding of software design patterns (e.g., MVVM, MVI) and expertise in building modular, scalable app architectures. * You have good knowledge of reactive programming (Flow, Coroutines and Concurrency). * You have a strong grasp of testing best practices: knowing what to test, why, and how to write resilient tests. * You strive for clean code, and you are flexible to balance pragmatism and perfection. * You have a keen interest in multi-platform development using Kotlin Multiplatform. WHY YOU SHOULD JOIN SUMUP (WARSAW) 🇵🇱 🌎 Opportunity to work , from our vibrant Warsaw office with inspiring art-filled lounges and a skyline terrace in the Mennica Legacy Tower.  🌈 Commitment to Diversity and Inclusion: be part of a workplace that values and promotes diversity, fostering an inclusive environment where everyone's perspectives are respected and embraced  🚀 Enrolment onto our VSOP program: you will own a stake in SumUp’s future success  🚴 Fitness support: work out on-site at our gym or explore the city using the Multisport Card, subsidised by SumUp for access to sports facilities across Warsaw  🩺 Commitment to well-being: access health insurance coverage for you and your family, plus life insurance to further protect your peace of mind  🏖️ Generous time off: enjoy 26 days of paid leave plus public holidays and special leave days 🌴 Break4me: 1-month sabbatical after 3 years of service  🔗 Referral Bonus: earn additional rewards by referring talented individuals to join the SumUp team *Disclaimer The stated salary range represents the expected compensation for candidates who meet the core requirements of this role. Offers above this range may be considered in exceptional circumstances, subject to internal review and approval, where a candidate's qualifications, skills, or experience significantly exceed the role's standard expectations.   Job Application Tip We recognise that candidates feel they need to meet 100% of the job criteria in order to apply for a job. Please note that this is only a guide. If you don’t tick every box, it’s ok too because it means you have room to learn and develop your career at SumUp.