Now hiring

Backend Development Engineer -CPaaS Business Department (RS Product Delivery & Innovation Div) @ Rakuten

Tokyo, JPOnsiteFull-time
Apply with ResuMinder

Opens on the employer's site

About this role

Job Description: About Organization We are building the next generation of our CPaaS platform, a robust ecosystem powering multi-channel communication services. Our platform supports global traffic across SMS, Email, Voice, WhatsApp, LINE, RCS, Passkey, and advanced Authentication services. We are looking for a highly skilled Backend Engineer to drive the scalability, reliability, and evolution of these services within a high-autonomy, fast-paced R&D environment.

Job Duties

• Backend Service Development: Design, implement, and optimize microservices powering multi-channel communication workloads.

• Feature Engineering: Build and enhance backend capabilities supporting messaging, identity, verification, and communication APIs.

• Distributed Systems Engineering: Develop high-throughput, low-latency services for global CPaaS traffic.

• Database Engineering: Design schemas, optimize queries, and ensure peak performance across databases.

• Cloud-Native Architecture: Deploy and operate services on Kubernetes, ensuring resilience, scalability, and cost-efficiency.

• API-First Engineering: Build clean, scalable REST APIs and contribute to API-first product architecture.

• CI/CD & GitOps: Manage version-controlled pipelines for build validation, automated testing, and safe deployments.

• AI-Enhanced Development: Utilize LLM-based tools (e.g., Claude, Codex) to improve code quality, automate documentation, and accelerate development workflows.

• Observability: Ensure system visibility using Grafana, Prometheus, and structured logging.

• Cross-Functional Collaboration: Partner with Product Managers, QA, DevOps/SRE, and UI/UX teams to deliver high-quality features.

• Engineering Excellence: Uphold coding standards, conduct code reviews, and drive continuous improvement of engineering practices.

Minimum Qualifications

• 5+ years of hands-on backend development experience.

• Strong proficiency in Java or Golang.

• Expertise with Postgres and MySQL.

• Hands-on experience with Kubernetes and containerization.

• Experience with CI/CD pipelines (GitHub Actions preferred).

• Experience with Microservices and API-first system design.

• AI-Assisted Development: Proficient in leveraging LLM-based tools for coding, automation, and workflow acceleration.

• Advanced English proficiency (strong communication, documentation, and collaboration skills).

Preferred Qualifications

• Domain experience with communication protocols (SMPP, SIP, REST APIs, WebRTC).

• Experience across multiple CPaaS domains (SMS, Email, Voice, Passkey, Auth Services, WhatsApp, LINE, RCS, etc.).

• Proven ability to work effectively in fast-moving, high-autonomy environments.

Key Interfaces

• Backend Engineering Team

• QA & Automation Teams

• DevOps / SRE

• Product Managers

• UI/UX Designers

• Project Managers

• R&D Leadership / CTO

Languages: English (Overall - 3 - Advanced)

Ready to apply?

Install the ResuMinder extension and we'll auto-fill the application in seconds — no rewriting.

See how your CV scores