About Appier 

Appier is a software-as-a-service (SaaS) company that uses artificial intelligence (AI) to power business decision-making. Founded in 2012 with a vision of democratizing AI, Appier’s mission is turning AI into ROI by making software intelligent. Appier now has 17 offices across APAC, Europe and U.S., and is listed on the Tokyo Stock Exchange (Ticker number: 4180). Visit www.appier.com for more information.

About the role

We are seeking a highly skilled Senior Backend Developer to join the Payable Ads team (https://www.appier.com/en/blog/what-is-playable-ads) with deep expertise in distributed systems and modern backend architecture. The ideal candidate will be responsible for designing and building scalable, high-performance backend services while maintaining clean, maintainable code and collaborating closely with cross-functional teams.

This role requires a strong understanding of microservices, messaging systems, data persistence layers, and system performance optimization.

Responsibilities 

• Architect and develop robust, scalable backend services and APIs using ASP.NET Core
• Design efficient, normalized database schemas and optimize data access logic  
• Implement message-driven communication with high reliability and fault tolerance  
• Take ownership of backend code quality, documentation, and maintainability  
• Proactively identify performance bottlenecks and implement scalable solutions  
• Collaborate with DevOps for containerization and deployment pipeline improvements  
• Explore and integrate AI-assisted development tools to boost productivity  
• (Optional) Contribute to low-level integrations through FFI for performance-critical components

About you 

[Minimum qualifications]

• Extensive experience in ASP.NET Core backend development, or proficiency in any one of programming languages (e.g., Java, Go) and willing to develop with C# .NET
• Advanced proficiency in C# programming and object-oriented principles  
• Proven experience in distributed systems and microservice architectures  
• Strong expertise in PostgreSQL, MongoDB, and familiarity with both SQL and NoSQL database design principles  
• Proficiency in code-first development and hands-on experience with Entity Framework Core or equivalent ORMs  
• Advanced knowledge of **RabbitMQ** or similar **message broker systems** (e.g., Kafka, NATS)  
• In-depth understanding of IO-bound operations, threading, parallelism, and asynchronous programming  
• Practical experience with Docker and container-based deployment workflows  
• Demonstrated ability to write clean, well-documented code and solve complex problems analytically  
• Strong abstract thinking and decision-making capabilities  
• Solid experience in performance tuning and designing scalable backend systems 
• Familiarity with and ability to leverage AI tools in development workflows  
• (Optional) Experience working with FFI (Foreign Function Interface) and integrating native code or libraries 

[Preferred qualifications]

• Solution-oriented mindset with a focus on system sustainability and maintainability  
• Ability to work independently and make high-level architectural decisions  
• Willingness to explore and integrate emerging technologies into backend systems  
• Strong collaboration and communication skills with technical and non-technical stakeholders

[Language]

Fluent in English, Japanese language proficiency is not required.

Open to overseas candidates/Visa Support
This position can be based in Tokyo, Japan or Taipei, Taiwan. For international candidates, Appier's Japan office provides visa sponsorship to ensure a smooth relocation transition to Japan.

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