Senior Software Engineer – Real-Time Conversational AI

Build the real-time technology powering the next generation of AI conversations. Our client, a fast-growing AI technology company in Japan, is looking for an experienced Senior Software Engineer to help build and scale its real-time conversational AI platform. Annual Salary: 750万円～1,600万円 / Hybrid / Remote work available The company develops an AI-powered communication platform that enables businesses to automate and transform customer interactions using voice AI and conversational technologies. The platform has already been adopted by tens of thousands of business accounts and continues to grow rapidly. As usage expands, the engineering team is facing increasingly sophisticated challenges around real-time communication, low-latency processing, scalability, reliability, and 24/7 availability. In this position, you will become one of the key technical contributors behind the conversational platform, helping design the next generation of its architecture while raising engineering standards across the team. What You Will Do Design and develop the core architecture of a real-time AI conversational platformBuild and improve low-latency voice communication systems using Python, asyncio and WebSocketImprove the architecture and functionality of the AI conversation engineDesign scalable and highly reliable APIs for a rapidly growing production environmentLead technical discussions and contribute to architecture and design decisionsConduct code reviews and design reviews to improve engineering quality across the teamIdentify technical debt and lead initiatives to improve system maintainability and performanceImprove observability and reliability of real-time conversational systemsWork closely with Product Managers and Designers to define technical specifications and deliver new product capabilitiesIntegrate the platform with external services and APIsLeverage AI coding agents and modern AI-assisted development tools to improve engineering productivityContribute to the evolution of the platform’s next-generation architecture Technical Environment Language: PythonFrameworks / Libraries: FastAPI, asyncio, WebSocketCloud & Infrastructure: AWS, Terraform, Amazon ECSDatabases: PostgreSQL, DynamoDBExternal Integrations: Twilio, REST APIsDevelopment Tools: GitHub, GitHub Actions, Slack, Notion, Linear Key Technical Challenges This is not a standard backend engineering position. The platform provides AI-powered voice conversations that must operate 24 hours a day, 365 days a year, making reliability and latency critical engineering challenges. You will work on areas such as: Real-time bidirectional communicationPersistent WebSocket connectionsAsynchronous processingLow-latency architectureHigh availability and fault toleranceLLM integration and redundancyProduction observabilityPerformance optimizationScaling real-time AI workloads Why Join? This is an opportunity to work on a technically challenging product where AI must interact with people in real time. Rather than simply integrating an LLM into a conventional application, you will tackle engineering challenges involving milliseconds of latency, persistent connections, reliability, scalability and 24/7 availability. You will have significant influence over technical decisions and help shape the architecture of a rapidly growing AI platform used by tens of thousands of businesses. If you are a strong Python engineer interested in real-time systems, Voice AI, LLMs and highly scalable platforms, this is an opportunity to build technology that can fundamentally change how businesses communicate with their customers. Requirements 5+ years of professional Python development experienceExperience developing and operating production services using web frameworks such as FastAPIStrong hands-on experience with asyncio, WebSocket, or similar asynchronous / persistent-connection technologiesExperience designing and developing APIs with scalability and reliability in mindStrong understanding of software architecture, testing, maintainability, and production operationsAbility to independently make technical decisions and take ownership from design through implementation and operationJapanese Business Level Who We Are Looking For Can independently make technical decisions in the Python ecosystemEnjoys solving complex engineering problems where there is no obvious answerCan act as a technical role model for other engineersTakes ownership beyond implementation, including architecture, testing, reliability, and operationsCan balance product speed with long-term technical qualityCommunicates proactively with Product Managers, Designers, and other engineersIs excited about adopting new development approaches, including AI coding agents and AI-assisted engineering workflowsWants to build technology at the intersection of AI, voice communication, and real-time distributed systems Benefits Compensation Annual Salary: 750万円～1,600万円Monthly salary: approximately ¥625K – ¥1.33MCompensation will be determined based on experience and skills.Stock options may also be offered depending on individual performance and contribution.Location & Working Style Tokyo or Osaka Hybrid / Remote work availableFlexible working hoursCore hours: 10:00 – 15:00Standard working day: 8 hoursFull-time permanent position3-month probation period with no change in compensation or benefits Benefits & Holidays Five-day work weekSaturdays, Sundays and national holidays offPaid annual leaveChildcare leaveSpecial / bereavement leaveFull social insuranceRemote / hybrid working environmentBook purchase supportInternal team events and other employee benefits