Senior Android Developer

Komoju Komoju

6d • Remote

About The Position

We are looking for our first Senior Android Developer to help build KOMOJU’s Point of Sale (POS) application and native mobile apps, which implements our Platform API for payment processing. As our first Android engineer, you will play a key role in defining coding standards, architectural decisions, and the frameworks we adopt. Our ideal candidate has strong experience building mobile applications and is eager to expand across languages and frameworks to deliver exceptional mobile experiences. Testing and code quality are central to our engineering culture, so a solid understanding of testing principles and methodologies is essential. We are not just looking for a standard mobile developer, but for a Systems-on-Android Engineer. You should have expert-level proficiency in Kotlin and Java, with the ability to write high-performance, thread-safe, and maintainable code. This position sits at the intersection of application logic and hardware integration. You will be responsible for integrating SDKs that control IC card readers, NFC modules, magstripe readers, and PIN pads. Success in this role requires experience with low-level hardware event handling, Android background service communication (AIDL/IPC), and complex state machine management. Knowledge of the EMV protocol and payment transaction flows is a plus. However, as EMV processing is specialized, we prioritize engineers with strong architectural discipline who can design robust, testable systems and quickly master hardware documentation.

Requirements

• Minimum 5+ years of experience.
• Experience with Android SDK and mobile development lifecycle.
• Familiarity with RESTful APIs to connect mobile applications to back-end services.
• Strong knowledge of mobile UI/UX principles, patterns, and best practices.
• Generalist (T-shaped developer), able to jump between multiple areas of our tech stack to get the job done.
• Ability to work effectively in a collaborative team environment.

Nice To Haves

• Some experience of iOS development and general familiarity with iOS architecture is welcomed.
• Experience working for a Japanese business.
• Lead and coach other members of the team, fostering skill development and high performance.
• Business-level proficiency in Japanese.
• Knowledge of cross-platform frameworks for iOS and Android is welcomed.

Responsibilities

• Develop KOMOJU POS, native merchant apps and mobile SDK offerings using Kotlin.
• Collaborate with product managers and other developers to define, design, and ship new features.
• Work across tech stacks with backend engineers to design and implement features for mobile applications.
• Flexibility to engage with other programming languages and work on our platform backend as needed.
• Technical design and architecture review across both mobile platforms (iOS and Android).

Benefits

• 10 days regular vacation, additional 5 days summer, and 5 days winter vacation
• Paid birthday holiday
• Budget for self-learning allowance, to ensure our employees’ skills remain current
• Access to the O’Reilly Learning Platform
• Language training for Japanese/ English
• Twice a week office lunch

What This Job Offers

• Job Type: Full-time
• Career Level: Senior
• Education Level: No Education Listed