Senior Software Engineer (LINE API / LIFF App)

We’re looking for a Senior Software Engineer based in Japan with hands-on experience using the LINE Messaging API and LIFF (LINE Front-end Framework). You’ll work closely with teams in the U.S. and Japan to design solutions, build messaging workflows that scale, and open new revenue channels for the business., We work like an agile startup inside Yahoo, with teammates around the world and a remote-first way of working. We’re looking for engineers who are:

• Self-Driven Owners: You take a feature from idea to production and keep improving it.
• Global Collaborators: You communicate proactively and in writing across time zones and cultures.
• Agile Thinkers: You ship small experiments, measure the results, and share what you learn with the team., * Design, build, and optimize LINE messaging services and applications on AWS, using AI coding agents (e.g., Claude Code, Copilot agent mode) as part of your daily work.
• Build new product features and internal tools for our global clients.
• Partner with cross-functional stakeholders to identify user pain points and translate business requirements into robust technical specifications.
• Deeply understand the architecture of our existing ad platform well enough to build smooth integrations and keep the system healthy.
• Continuously enhance core components of the whole ecosystem for improved performance and scalability., * Overlapping Hours: Engineering team are based in both Japan and the United States, this role requires working from 6:00 AM JST (Tuesday through Friday) to maintain sufficient overlapping hours with U.S. based colleagues. Mondays follow standard local working hours.
• Work Arrangement: This position is primarily remote (work-from-home), with occasional in-office meetings or team gatherings in Japan.

• Bachelor’s degree in Computer Science or a related field, or equivalent practical experience.
• 8+ years of professional experience in software development.
• Deep hands-on experience with the LINE Messaging API and LIFF, plus proven experience building and launching LINE MINI Apps, including LINE SDKs and LINE Login/authentication flows.
• Strong programming proficiency with Java, JavaScript, and TypeScript
• Experience designing REST APIs and running containerized (Docker) applications on AWS or GCP in Linux environments.
• Solid grounding in object-oriented design, concurrency, and distributed systems.
• Strong foundation in algorithms and data structures, with hands-on experience in relational databases (e.g., MySQL, Oracle) and/or large-scale data stores (e.g., BigQuery).
• Experience with other LINE APIs is a plus.

Soft Skills & Communication:

• Excellent technical analysis, problem-solving, and communication skills.
• Proactive mindset with a strong sense of end-to-end ownership.
• Business-level Japanese and English, both spoken and written.

Boundless Inc., part of Yahoo Inc (headquartered in the U.S.), is a trusted marketing and advertising partner empowering global companies to succeed in the Japanese market. With multilingual teams spanning key regions worldwide, we deliver end-to-end solutions driven by deep local insights and a global perspective., At Boundless, we know that diversity makes us stronger. We are committed to a collaborative, inclusive environment that encourages authenticity and fosters a sense of belonging. We strive for everyone to feel valued, connected, and empowered to reach their potential and contribute their best.

Yahoo has a high degree of flexibility around employee location and hybrid working. In fact, our flexible-hybrid approach to work is one of the things our employees rave about. Most roles don’t require specific regular patterns of in-person office attendance. If you join Yahoo, you may be asked to attend (or travel to attend) on-site work sessions, team-building, or other in-person events. When these occur, you’ll be given notice to make arrangements.

If you’re curious about how this factors into this role, please discuss with the recruiter.