Senior Software Engineer, Backend Development (Playable Ads)

About Appier 

Appier is an AI-native Agentic AI as a Service (AaaS) 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

Appier's Playable Ads team (https://www.appier.com/en/blog/what-is-playable-ads) builds AI-powered playable and video ad experiences that drive dramatically higher engagement and conversion for the world's leading apps and games. We're looking for a Senior Backend Developer with deep expertise in distributed systems and modern backend architecture to design and build the scalable, high-performance services behind these experiences — from creative generation pipelines to the infrastructure that brings our ML models to production. You'll work across microservices, messaging systems, data persistence layers, and system performance optimization, while partnering with ML scientists on MLOps workflows to continuously ship and serve new model versions to end users. You'll also collaborate closely with frontend engineers and product managers to deliver seamless, cross-functional outcomes.

If you're passionate about building backend systems that operate at scale, thrive in cross-functional teams, and want your code to directly power AI-driven ad experiences reaching millions of users, we'd love to talk.

What You'll Work On

• Architect and develop robust, scalable backend services and APIs using ASP.NET Core, owning sizable projects from system design through production operation.
• Design efficient database schemas and optimize data access logic across SQL and NoSQL data stores.
• Implement message-driven communication with high reliability and fault tolerance.
• Partner with ML scientists to build and maintain MLOps pipelines — including model versioning, deployment, serving, and monitoring — ensuring new models are reliably delivered to production.
• Lead system designs, drive technical roadmap decisions, and provide guidance to team members.
• Proactively identify performance bottlenecks, profile critical components, and implement scalable solutions.
• Own and continuously improve system observability, incident management, CI/CD pipelines, and deployment workflows.
• Explore and integrate AI-assisted development tools and emerging technologies to boost team productivity.
• Participate in on-call rotation to ensure product reliability and scalability.

What We're Looking For 

[Minimum qualifications]

• Proficiency in C# and ASP.NET Core, or experience with other object-oriented languages (e.g., Java, Go) with willingness to cross-train in the .NET stack.
• Proven experience in distributed systems, microservice architectures, and designing scalable backend systems.
• Strong expertise in PostgreSQL, MongoDB, or equivalent SQL/NoSQL databases, with hands-on experience in ORM frameworks such as Entity Framework Core.
• Advanced knowledge of message broker systems such as RabbitMQ, Kafka, or NATS.
• In-depth understanding of IO-bound operations, threading, parallelism, and asynchronous programming.
• Practical experience with Docker, container-based deployment workflows, and cloud platforms (AWS, GCP, or Azure).
• Hands-on experience with CI/CD pipelines, observability tooling, and production operational practices.
• Demonstrated ability to write clean, well-documented code and solve complex problems analytically.
• Clear communicator who can explain technical decisions to both technical and non-technical stakeholders and enjoys working in a fast-paced, collaborative environment.
• Proficient in using LLM-powered development tools (e.g., GitHub Copilot, Cursor, ChatGPT) to accelerate productivity.

[Preferred qualifications]

• BS/MS degree in Computer Science or a related field.
• Experience with MLOps practices such as model serving infrastructure, A/B testing frameworks, or ML pipeline orchestration tools.
• Leadership experience such as mentoring junior engineers, leading code reviews, or facilitating agile processes.
• Experience with performance profiling and debugging tools, high-performance network services, or FFI integrations for performance-critical components.
• Solution-oriented mindset with a focus on system sustainability, and willingness to explore emerging technologies into backend systems.

[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.

#LI-AK1