Description
本ポジションは日本語JDの用意がありません。

Senior Software engineer, iOS (AI/LLM) - Mercari

• Employment Status: Full-time
• Work Hours: Full Flextime (no core time)
• Office: Roppongi

For more details, see the Overview of Our Positions section on our Careers site.

About Mercari
Circulate all forms of value to unleash the potential in all people
"What can I do to help society thrive with the finite resources we have?" The Mercari marketplace app was born in 2013 out of this thought by our founder Shintaro Yamada as he traveled the world. We believe that by circulating all forms of value, not just physical things and money, we can create opportunities for anyone to realize their dreams and contribute to society and the people around them. Mercari aims to use technology to connect people all over the world and create a world where anyone can unleash their potential. For more information about Mercari Group's mission, see Mercari's Culture Doc

Organization/Team Mission

Mercari Engineering Principles
Mercari Engineering Principles are a shared understanding that serves as the foundation of engineering beliefs and behavior at Mercari. The Engineering Principles are designed to complement the organizational identity (Mercari's mission, values, and culture) from an engineering viewpoint.

These principles ultimately help us achieve Mercari's mission by defining the ideal state we seek to realize in the long term.

• Passion For The Product
• Grow Together
• Solve Through Mechanisms
• Collaborate Openly

For More Details, Please See The Following Link

• Engineering Culture

The AI / LLM Team's mission is focused on two core pillars, "building" and "enabling" – delivering new AI-driven features and user experiences to maximize product-facing impact for Mercari's business. We do this both through independent initiatives owned by our team, as well as by horizontally collaborating with product and engineering teams across the entire organization

As an iOS engineer, you will work on building features with our machine learning, backend, and infrastructure members as well as collaborating with other feature-owner iOS engineering teams.

See here for more information about our mission and values.

Work Responsibilities

• Design, implement, and maintain high-quality iOS features using Swift and modern iOS frameworks.
• Own end-to-end feature development, from requirements definition through architecture, implementation, testing, and release.
• Lead architectural design for complex features and system components, ensuring maintainability, scalability, and reliability.
• Optimize app performance, startup time, memory usage, and stability across diverse devices and OS versions.
• Work closely with machine learning, backend, infrastructure, product, and design teams to deliver seamless mobile experiences, as well as other feature-owner iOS engineering teams.
• Contribute to and evolve Mercari's mobile platform, SDKs, and shared modules used across teams.
• Drive high code quality through code reviews, automated testing, CI/CD improvements, and rigorous documentation.
• Champion engineering best practices and contribute to guidelines and standards across Client Engineering.
• Stay current with the latest developments in iOS, Swift, UIKit, SwiftUI, concurrency, and mobile architecture patterns.
• Bring innovative ideas to improve user experience, developer experience, and operational efficiency.
• Take ownership of initiatives that span multiple teams, driving alignment and technical decision-making.
• Mentor junior and mid-level engineers, helping strengthen the overall technical capabilities of the team.

Unique Challenges

• In this position, you will develop iOS features for AI-driven solutions that leverage Mercari Group's vast data assets, creating high-impact user experiences for tens of millions of users.
• Deliver highly performant and reliable functionality in a fast-paced environment with complex product requirements.
• Bridge consumer-grade UX expectations with robust engineering architecture and infrastructure.
• Influence platform-wide technical strategy, shaping the future direction of Mercari's mobile ecosystem.
• Lead cross-functional efforts in ambiguous problem spaces where user needs and technical constraints must be balanced.

Qualifications- Required Experience/Skills

• Shared belief in the mission and values of the Mercari Group.
• Bachelor's degree in Computer Science, Engineering, or equivalent practical experience.
• Strong proficiency in Swift and iOS development frameworks (UIKit, SwiftUI, Combine, Foundation).
• Solid understanding of mobile architecture patterns (MVC, MVVM, Clean Architecture, VIPER, etc.).
• Demonstrated experience with large-scale mobile applications and complex codebases.
• Experience integrating with backend APIs and asynchronous/concurrent programming.
• Strong analytical and problem-solving skills; ability to navigate ambiguity.
• Excellent communication skills and ability to explain technical concepts clearly.
• Passion for building user-facing mobile products.

• Preferred Experience/Skills

• Experience with large-scale mobile apps serving millions of users.

• Expertise in performance optimization, instrumentation, and mobile observability (e.g., crash analysis, metrics).
• Experience with SwiftUI, concurrency (async/await), and modern iOS platform capabilities.
• Contributions to open-source iOS projects or active involvement in the mobile community.
• Experience driving technical initiatives across multiple teams or owning platform-level components.
• Familiarity with CI/CD for mobile, automated testing frameworks, and release management.

• UI/UX sensitivity and an eye for detail in crafting polished user experiences.

• Language

• English: Independent (CEFR B2) Required

• Japanese: Independent (CEFR B2) Optional

For details about CEFR, see here.

Learn More About Mercari Group

• Careers site:
• Mercan:
• Social media: X / Linkedin

Recruiting at Mercari

At Mercari Group, we value empathizing with and embodying the mission and values of the Group and each company. To promote the creation of an organization that maximizes the total amount of value exhibited by all members, we would like to understand the experience and skills of each candidate as accurately as possible.

Recruiting cycle at Mercari Group

• Application screening
• Skill assessment: For engineering positions, you will be asked to complete a skill assessment on HackerRank or GitHub. For non-engineering positions, you may be asked to complete an assessment depending on the position. (The timing of the assessment may coincide with the interview process.)
• Interview: The number of interviews may vary depending on the position.
• Reference check: We will ask for online references around the timing of the final interview.
• Offer: Offers will be determined carefully in consideration of the final interview and the reference check.

Learn more about our recruiting process here.

Equal Opportunity Hiring

Here at Mercari, we work to realize a world in which no one's potential is limited by their background and everyone has the opportunity to freely create value. We also firmly believe that a mindset of Inclusion & Diversity is essential for us to achieve our mission.

This, of course, extends to our hiring practices as well. Mercari is committed to eliminating discrimination based on age, gender, sexual orientation, race, religion, physical disability, and other such factors so that anyone who shares our mission and values can join us, regardless of their background. For more details, please read our I&D statement.

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