Job Description: About Organization The Architecture Review Board (ARB) acts as the final technical gatekeeper for every High-Level Design (HLD) within the Rakuten Mobile network. Our mission transcends basic technical feasibility; we analyze solutions through a multi-angle lens, including strategic necessity, security, infrastructure optimization, and competitive benchmarking. We are currently spearheading two major initiatives: Tech SLM: A proprietary, AI-powered platform utilizing advanced LLM fine-tuning and high-precision RAG pipelines to automate design reviews and knowledge management. AI Council: A dedicated authority established to enforce audit frameworks, standardized design patterns, and cross-functional synergy for AI use cases across Rakuten Mobile. The ARB serves as a major stakeholder alongside Security and AIDD teams to ensure network stability and integrity. Why Join Us Ultimate Tech Authority: Define blueprints, safety guidelines, and architectural guardrails for an entire cloud-native mobile network. Build Proprietary AI Assets: Go beyond basic APIs; fine-tune foundation models on massive, specialized telecom datasets. Solve RAG at Scale: Design high-precision, low-latency semantic search systems to eliminate hallucinations in complex network documentation. High-Impact Ownership: Prevent vendor lock-in and secure network stability while driving the transition toward an autonomous, AI-driven network. Job Duties Tech SLM Engineering: Build the proprietary Tech SLM platform using advanced LLM fine-tuning and high-precision RAG pipelines to automate HLD creation and design reviews. Strategic AI Governance: Serve on the AI Council to validate use cases, set standardized design patterns, and enforce network-wide architectural guardrails. Algorithmic & Model Assessment: Evaluate open-source or proprietary models against strict telecom network performance, safety, and latency metrics. ML Infrastructure Review: Audit and review existing AI/ML infrastructure to provide design optimizations that streamline workloads and significantly reduce infrastructure usage. Vendor Auditing & Integration: Scrutinize third-party AI tools and agentic frameworks to ensure secure integration while preventing vendor lock-in. Architectural Guardrails: Define standardized architectural disciplines, design patterns, and best practices for AI/ML implementation across the network. Operational Integrity: Establish comprehensive monitoring frameworks to track model performance, safety, and data governance. Ecosystem Integration: Ensure seamless, secure, and low-latency integration of AI services within the existing Rakuten Mobile network stack. Minimum Qualifications Bachelor’s degree in Computer Science, AI, Machine Learning, Data Science, Telecommunications Engineering, or a related field. 7+ years of total industry experience. 3+ years of experience in application/software design and architecture with AI/ML, including hands-on Generative AI implementation and model design. Strong expertise in LLMs/SLMs, fine-tuning techniques, RAG, vector databases, and prompt engineering. Experience designing and deploying scalable AI solutions using Python, cloud platforms, and Kubernetes. Solid understanding of AI governance, responsible AI practices, security, and data privacy. Basic understanding of Telco networks, Cloud, and networking technologies. Proficiency in English. Preferred Qualifications Master’s degree in Computer Science, Data Science, or AI/ML fields. 7–15 years of total experience, with at least 3 years in AI/ML design and implementation. Experience in telecommunications, mobile network architecture, autonomous networks, and related AI use cases. Hands-on expertise with advanced LLM optimization (LoRA, QLoRA, model distillation) and agentic AI frameworks. Experience building enterprise AI platforms, AI copilots, or domain-specific language models. Strong knowledge of MLOps, AI observability, model monitoring, and lifecycle management tools. Proven ability to establish AI governance frameworks and assess third-party AI vendors. Relevant certifications (AWS, Azure, GCP, NVIDIA, or equivalent). Japanese language skills are an additional advantage. Languages: English (Overall - 3 - Advanced) Looking for members to join our mobile phone business “They cannot succeed if they step into the field at this late date” Some people say Rakuten is reckless in trying to enter the mobile communications business. However, innovation is realized if we succeed when something seems impossible. At Rakuten, we think the world changes when we achieve such changes. Because our history has always been a series of innovations since our establishment. Launching a communication carrier is an opportunity that we have once in our lives. Crack open the current communication industry. Blow new wind into life. Why not create innovation with us? Why not do something big? Job Opening: Regular Employee Company Name Rakuten Mobile, Inc. Qualifications [Required] TOEIC score of 600 or equivalent English proficiency/skills. Rakuten Group Englishnization Rakuten Mobile, Inc. aims for all employees to achieve a TOEIC score of 800 or higher, in line with Rakuten Group, Inc.'s Englishnization policy. As a first step, a TOEIC score of 600 (or equivalent English proficiency) is required for mid-career hires. Job Responsibilities [Upon initial hiring] Varies depending on the position. The scope of work changes may include assignments to other duties determined by the company based on directives, etc. (If a transfer is ordered in accordance with the secondment regulations, the duties will be those of the seconded company.) Contract Period No fixed term Probationary Period Yes (3 months) The probationary period may be extended at the company's discretion. Employment conditions will not change during the probationary period. Work Location [Upon initial hiring] Headquarters (Rakuten Crimson House, 1-14-1 Tamagawa, Setagaya-ku, Tokyo), and other business sites. The scope of work location changes may include reassignments or transfers to locations nationwide and overseas. If remote work is partially permitted, the work location will be the remote work location approved by the company. The work location at the time of hiring will be communicated in the job description for each position and the offer letter. As a measure against passive smoking, smoking is prohibited on the premises of Rakuten Crimson House (however, this may vary depending on the business site). Working Hours Standard working hours: 9:00 AM - 5:30 PM On days when Rakuten Group morning meetings are held, the prescribed working hours will be 8:00 AM - 4:30 PM. Prescribed working hours are 7.5 hours, with a 1-hour break. A flextime system is partially applied. Core time: 11:00 AM - 3:00 PM (8:00 AM - 12:00 PM on morning meeting days) Some positions may differ from the above; details will be specified in the offer letter (e.g., application of discretionary labor system). Overtime work or work on holidays may be instructed. Holidays/Leave/Absence Complete two-day weekend system (Saturday and Sunday) and national holidays Summer vacation, New Year's holiday, annual paid leave, menstrual leave, special leave (condolence, volunteer, etc.) Maternity leave, childcare leave, family care leave Some positions may differ from the above; details will be specified in the offer letter. Salary Monthly salary: JPY300,000 ~ (Breakdown: Base salary JPY 227,848 + fixed overtime pay for 40 hours JPY 72,152) The above is the minimum salary offered for mid-career hires. Overtime work exceeding 40 hours per month will be paid separately as overtime allowance. Some positions may differ from the above; details will be specified in the offer letter (e.g., application of discretionary labor system). Commuting allowance will be provided (conditions and maximum amount apply). Salary Increase Yes Reviewed in January and July based on company performance and individual evaluation. Bonus Yes Paid in June and December based on company performance and individual evaluation. Stock Option Plan Yes Retirement Allowance Yes Insurance Employees' Pension Insurance, Health Insurance, Workers' Accident Compensation Insurance, Employment Insurance, etc. Benefits Cafeteria (breakfast, lunch, dinner generally free) Employee Stock Ownership Plan English learning support, etc. Job Opening: Fixed-term Employee Company Name Rakuten Mobile, Inc. Qualifications Varies depending on the recruiting position. Job Responsibilities [Upon initial hiring] Varies depending on the recruiting position. The scope of work changes may include assignments to other duties determined by the company based on directives, etc. (If a transfer is ordered in accordance with the secondment regulations, the duties will be those of the seconded company.) Contract Period Fixed term Maximum contract renewal period: Yes (The total contract period is 5 years, starting from the initial employment contract date.) Probationary Period None Work Location [Upon initial hiring] Headquarters (Rakuten Crimson House, 1-14-1 Tamagawa, Setagaya-ku, Tokyo), and other business sites. The scope of work location changes may include reassignments or transfers to locations nationwide and overseas. If remote work is partially permitted, the work location will be the remote work location approved by the company. The work location at the time of hiring will be communicated in the job description for each position and the offer letter. As a measure against passive smoking, smoking is prohibited on the premises of Rakuten Crimson House (however, this may vary depending on the business site). Working Hours Standard working hours: 9:00 AM - 5:30 PM On days when Rakuten Group morning meetings are held, the prescribed working hours will be 8:00 AM - 4:30 PM. Prescribed working hours are 7.5 hours, with a 1-hour break. A flextime system is partially applied. Core time: 11:00 AM - 3:00 PM (8:00 AM - 12:00 PM on morning meeting days) Some positions may differ from the above; details will be specified in the offer letter (e.g., application of discretionary labor system). Overtime work or work on holidays may be instructed. Holidays/Leave/Absence Complete two-day weekend system (Saturday and Sunday) and national holidays Summer vacation, New Year's holiday, annual paid leave, menstrual leave, special leave (condolence, volunteer, etc.) Maternity leave, childcare leave, family care leave Some positions may differ from the above; details will be specified in the offer letter. Salary Determined individually based on experience, etc. Commuting allowance will be provided (conditions and maximum amount apply). Salary Increase Yes Upon contract renewal, a salary revision may be proposed based on the most recent evaluation. Bonus May be paid taking into account company performance, general economic conditions, and work performance/abilities. Stock Option Plan None Retirement Allowance None Insurance Employees' Pension Insurance, Health Insurance, Workers' Accident Compensation Insurance, Employment Insurance, etc. Benefits Cafeteria (breakfast, lunch, dinner generally free) Employee Stock Ownership Plan English learning support, etc.

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