Backend Engineer

• Senior Product Engineer, Backendとしての行動を期待され、仕様策定からデリバリーの完遂に一気通貫で責任を持つ
• 定義フェーズから主体的に踏み込み、プロダクトスペックの具体化・合意形成・品質/計測の成立・リリースまで自律的にリードする
• GoによるMicroserviceおよびAPIの設計・開発・運用
• Protocol Buffers + gRPC を用いたマイクロサービス間のI/F設計
• アプリケーション要件に基づいたアーキテクチャの設計、ミドルウェアの選定
• マイクロサービスのパフォーマンスチューニング、モニタリング、アラート対応を通じたシステムの信頼性向上
• ユーザーの行動ログなどの定量的・定性的な分析による施策の効果測定とサービス改善
• 決済、与信、会計、本人確認（KYC）領域における複雑なドメイン課題に対する高い正確性と拡張性を両立したシステム設計

Senior Product Engineer, Backend

• GoによるMicroservice（マイクロサービス）およびAPIの設計・開発・運用
• Protocol Buffers + gRPC を用いたマイクロサービス間のI/F設計
• アプリケーション要件に基づいたアーキテクチャの設計、ミドルウェアの選定
• マイクロサービスのパフォーマンスチューニング、モニタリング、アラート対応を通じたシステムの信頼性向上
• ユーザーの行動ログなどの定量的・定性的な分析による施策の効果測定とサービス改善
• 決済、与信、会計、本人確認（KYC）領域における複雑なドメイン課題（法的要件や厳格なデータ整合性を含む）に対する、高い正確性と拡張性を両立したシステム設計

Senior Software Engineer, Backend

Android Engineer

• メルカリ Android アプリ上の広告関連機能の設計・実装・保守
• 広告枠・広告表示・計測まわりの Android クライアント実装、および広告体験の品質向上
• 要件定義から設計・実装・テスト・リリースまで、機能開発のエンドツーエンドの推進
• モジュラーアーキテクチャに沿った、保守性・拡張性の高い設計
• 広告バックエンド・ML／検索・インフラ・プロダクト・デザイン各チームとの協働
• コードレビュー・自動テスト・CI/CD 改善・ドキュメント整備を通じた品質向上

Product Engineer, Android – Ads

• Build backend services, APIs and workflows for the AI Neobank app.
• Support products across insurance, payments, wallet, savings, investing, travel and financial services.
• Design reliable systems for user accounts, transactions, partner integrations, reconciliation, notifications and operations.
• Work with product and mobile teams to ship customer-facing journeys quickly.
• Integrate with banks, payment gateways, insurers, data providers and other partners.
• Improve system reliability, observability, security and performance.
• Build systems that are practical, auditable and ready for regulated financial products.

Backend Software Engineer – AI Neobank App

• Build backend services and APIs for onboarding, accounts, payments, cards, transfers, rewards, travel, FX, KYC and risk flows.
• Design reliable systems that can support real customer transactions, operational workflows and future financial products.
• Integrate with internal systems, financial partners, payment providers, AI services and third-party platforms.
• Own backend quality across reliability, security, latency, observability, data integrity and incident handling.
• Work with product, frontend, mobile and AI teams to launch features quickly and safely.
• Improve existing systems by simplifying flows, removing manual work and automating repeatable processes.

Backend Developer

Software Engineer

• Build mobile features across Android, iOS or cross-platform flows depending on your strength.
• Create clean journeys for onboarding, accounts, payments, cards, transfers, rewards, travel, FX and AI-assisted features.
• Work from product problem to shipped mobile experience, not just assigned screens.
• Collaborate with backend, design, product and AI teams to launch reliable customer-facing features.
• Improve app quality through production feedback, analytics, crash reports and user behaviour.
• Help raise the standard for mobile UX, reliability and speed across the product.

Mobile Application Developer – Japan

• Build and ship native iOS features for onboarding, accounts, cards, payments, transfers, rewards and AI-assisted user journeys.
• Make complex financial flows feel clean, fast and simple on mobile.
• Work with product, design, backend and AI engineers to take ideas from rough concept to production release.
• Own app quality across performance, crash rate, loading states, edge cases, responsiveness and release stability.
• Use production feedback, analytics and customer behaviour to improve features after launch.
• Integrate APIs, authentication, secure data handling and financial workflows with strong attention to reliability.

iOS Developer

Full-stack Engineer

• Build and ship full product features across frontend, backend, APIs and databases.
• Create customer and internal workflows for onboarding, accounts, payments, rewards, travel, FX, support automation, KYC and risk.
• Turn ambiguous product problems into working systems with clean UX and reliable backend logic.
• Work closely with product, design, mobile, backend and AI engineers to launch fast and improve after release.
• Build internal tools and automation that reduce manual work and help teams operate at scale.
• Own your work beyond release: monitor, debug, learn and improve.

Full Stack Engineer

• Build and ship native Android features for onboarding, accounts, cards, payments, transfers, rewards and AI-assisted user journeys.
• Turn complex financial flows into simple, fast and reliable mobile experiences.
• Work closely with product, design, backend and AI engineers to take features from idea to production.
• Own app quality across performance, crash rate, loading states, edge cases and release stability.
• Use production feedback, analytics and customer behaviour to improve what you build after launch.
• Integrate APIs, authentication, secure data handling and financial workflows with strong attention to reliability.

Android Developer

• メルカリグループのあらゆる決済を支える汎用基盤の設計から運用まで担う
• 分散トランザクションの整合性・可用性・レイテンシのトレードオフを設計する
• 金融水準の信頼性を満たす設計が求められる
• 汎用基盤としての設計を行う
• 外部決済プロバイダとの接続を設計する
• 大規模トラフィックの安定処理を維持する

Software Engineer, Backend – Payment Core

• GoによるMicroservice開発、API開発
• Protocol Buffers + gRPC を用いたマイクロサービス間のI/F設計
• ユーザーの行動ログなどの定量的・定性的な分析による施策の効果測定とサービス改善
• アプリケーション要件に基づいたアーキテクチャの設計、ミドルウェアの選定
• マイクロサービスのパフォーマンスチューニング、モニタリング、アラート対応

Software Engineer, Backend - Payment Platform

• Build backend services, APIs and workflows for the finance super app.
• Design reliable systems for user accounts, transactions, partner integrations, reconciliation, notifications and operations.
• Work with product and mobile teams to ship customer-facing journeys quickly.
• Integrate with banks, payment gateways, insurers, data providers and other partners.
• Improve system reliability, observability, security and performance.
• Build systems that are practical, auditable and ready for regulated financial products.

Backend Software Engineer – Finance Super App

• Build and ship Android features using Kotlin.
• Create clean mobile flows for insurance, payments, claims, renewals and financial services.
• Work with product and design to simplify complex user journeys.
• Integrate backend APIs and ensure mobile flows are stable, secure and reliable.
• Improve app performance, crash rate, loading states, responsiveness and memory usage.
• Use analytics, user behaviour and production issues to improve the product.
• Build AI-assisted mobile experiences only where they genuinely improve the user journey.

Android Software Engineer – Finance Super App

• Design, develop and ship high-quality Android applications using Kotlin.
• Build intuitive mobile experiences across insurance, payments, claims, renewals and financial services.
• Collaborate closely with product managers, designers and backend engineers to deliver seamless end-to-end user experiences.
• Integrate backend APIs while ensuring application stability, scalability and reliability.
• Optimize application performance, reducing ANRs, crashes, memory usage and battery consumption.
• Use analytics, production insights and customer feedback to continuously improve the product.
• Build AI-assisted mobile experiences where they provide meaningful value for users.
• Contribute to engineering best practices through code reviews, testing and continuous improvement.

Software Engineer, Android

• Design, develop and maintain high-performance native Android applications using Kotlin.
• Build intuitive user experiences across insurance, payments, claims, renewals and financial services.
• Work closely with product managers, designers and backend engineers to deliver seamless native mobile experiences.
• Integrate backend APIs while ensuring application stability, responsiveness and scalability.
• Optimize app startup time, rendering performance, ANR rates, crash rates, memory usage and battery efficiency.
• Continuously improve code quality through testing, code reviews and engineering best practices.
• Build AI-assisted native mobile experiences where they provide genuine value for users.
• Stay up to date with the latest Android platform capabilities and recommend improvements that enhance product quality.

• Develop and deliver Android features using Kotlin.
• Build intuitive mobile experiences across insurance, payments, claims, renewals and financial services.
• Work closely with product managers, designers and backend engineers to simplify complex user journeys.
• Integrate backend APIs and ensure mobile applications remain stable, reliable and performant.
• Improve app performance by reducing ANRs, crashes, memory consumption and battery usage.
• Use analytics, production insights and user feedback to continuously improve the product.
• Build AI-assisted mobile experiences where they genuinely enhance the user journey.
• Write clean, maintainable and well-tested code while contributing to code reviews and engineering best practices.

Android Developer – Finance Super App

• Build and ship high-quality iOS features using Swift.
• Develop intuitive mobile experiences across insurance, payments, claims, renewals and financial services.
• Work closely with product managers, designers and backend engineers to simplify complex user journeys.
• Integrate backend APIs and ensure mobile applications remain stable, scalable and reliable.
• Continuously improve application performance, crash rates, loading speed, responsiveness, memory usage and battery efficiency.
• Use analytics, production insights and user feedback to continuously improve product quality.
• Build AI-assisted mobile experiences where they create meaningful value for users.
• Contribute to engineering standards, code reviews and continuous improvement across the mobile platform.

Software Engineer, iOS

iOS Engineer

• Build and ship high-quality native iOS features using Swift.
• Develop intuitive mobile experiences across insurance, payments, claims, renewals and financial services.
• Work closely with product managers, designers and backend engineers to simplify complex user journeys.
• Integrate backend APIs and ensure mobile applications remain stable, scalable and reliable.
• Continuously improve application performance, crash rates, loading speed, responsiveness, memory usage and battery efficiency.
• Use analytics, production insights and user feedback to continuously improve product quality.
• Build AI-assisted mobile experiences where they create meaningful value for users.
• Contribute to engineering standards, code reviews and continuous improvement across the native iOS platform.

• Design, build and ship high-quality mobile features for iOS or Android.
• Develop intuitive mobile experiences across insurance, payments, claims, renewals and financial services.
• Work closely with product managers, designers and backend engineers to simplify complex user journeys.
• Integrate backend APIs and ensure mobile applications remain stable, scalable and reliable.
• Continuously improve application performance, crash rates, loading speed, responsiveness, memory usage and battery efficiency.
• Use analytics, production insights and user feedback to continuously improve product quality.
• Build AI-assisted mobile experiences where they create meaningful value for users.
• Contribute to engineering standards, code reviews and continuous improvement across the mobile platform.

Mobile Software Engineer

• Build and ship high-quality mobile applications for iOS or Android.
• Develop intuitive mobile experiences across insurance, payments, claims, renewals and financial services.
• Work closely with product managers, designers and backend engineers to simplify complex user journeys.
• Integrate backend APIs and ensure mobile applications remain stable, scalable and reliable.
• Continuously improve application performance, crash rates, loading speed, responsiveness, memory usage and battery efficiency.
• Use analytics, production insights and user feedback to continuously improve product quality.
• Build AI-assisted mobile experiences where they create meaningful value for users.
• Contribute to engineering standards, code reviews and continuous improvement across the mobile platform.

Software Engineer jobs in Japan

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