Job Description:

Business Overview

Rakuten is a leading Japanese e-commerce and internet services company that offers a wide range of products and services to customers worldwide. With a strong focus on innovation, Rakuten aims to empower individuals, businesses, and society as a whole through its unique ecosystem of e-commerce, fintech, digital content, and communications services.

Department Overview

The Merchandising and Advertisement Department leverages AI-driven advertisement optimization, and pricing and inventory optimization systems based on demand forecasting. By closely integrating the information obtained from merchandising into our advertisement strategies, we maximize the synergy between both functions. This enables us to efficiently deliver optimal offers and information to our customers, thereby contributing to increased sales and enhanced customer satisfaction.

The Advertisement Optimization Group is a team of specialists in ad optimization, with AI at its core. We are responsible for the development and operation of highly effective ad optimization logic and platforms.

Our mission is to maximize publishers' ad revenue while maintaining and improving advertisers' ROAS (Return On Ad Spend). Specifically, we continuously improve ad delivery optimization, bidding/budget allocation, personalization, and performance measurement, contributing to the realization of a world that enhances both advertisers' ROI (Return On Investment) and user experience.

Position:

Position Details
We are looking for a Senior Software Engineer to lead the design, development, and optimization of complex data processing pipelines and high throughput APIs. You will guide technical decisions, mentor engineers, and ensure that our platforms remain robust, scalable, and aligned with long-term business goals. This role is ideal for individuals who thrive in highly technical environments and enjoy solving challenging problems with modern engineering practices.

Responsibilities
- Lead the design and architecture of large-scale, distributed software systems.
- Develop high-quality, maintainable code across the full SDLC.
- Collaborate with product, design, and engineering stakeholders to define technical requirements and project scope.
- Drive engineering best practices including code reviews, testing strategies, standards, and documentation.
- Mentor and support junior/mid-level engineers through guidance, pairing, and knowledge sharing.
- Identify and resolve complex issues related to performance, scalability, and system reliability.
- Contribute to long-term technical strategy, platform modernization, and technology roadmap planning.
- Evaluate and integrate new tools, frameworks, and technologies to improve development efficiency.
- Experience leading technical initiatives, migration projects, or cross-team engineering efforts.

Mandatory Qualifications:
- Bachelor’s or Master’s degree in Computer Science, Engineering, or equivalent experience.
- 10+ years of professional software engineering experience.
- Deep expertise in at least one modern language (e.g., Python, Java, Go).
- Strong understanding of system design, distributed systems, microservices, and cloud architectures.
- Experience with REST APIs, event-driven systems, and asynchronous processing.
- Proven experience developing and deploying applications on GCP.
- Strong competency in data structures, algorithms, and software design patterns.
- Hands-on experience with CI/CD, testing frameworks, and Git-based workflows.
- Ability to navigate technical ambiguity, make sound architectural decisions, and clearly articulate technical trade-offs to both technical and non-technical audiences.

Desired Qualifications:

- Experience with Docker, Kubernetes, or other container orchestration tools.

- Background in high-availability or mission-critical systems.

- Knowledge of SQL/NoSQL databases, caching strategies, and data pipelines.

- Familiarity with observability tools (Prometheus, Grafana, ELK, OpenTelemetry).

- Exposure to security best practices, secure coding, and compliance requirements.

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Senior Software Engineer, Advertisement Optimization Group - Merchandising and Advertisement Department (MAD)