Senior / Principal Python Engineer

Join a project where scalable backend engineering meets modern AI-driven financial technology. We are looking for a Senior / Principal Python Engineer to help build and evolve high-load payment and revenue systems used by businesses worldwide. You will work on cloud-native backend services, distributed systems, and payment infrastructure while collaborating with Product, Frontend, AI, and Engineering teams. This role is ideal for engineers who enjoy solving complex technical challenges, influencing architecture decisions, and driving engineering excellence. We at Sigma Software value technical ownership, collaboration, and continuous learning. You will join an international environment where innovation, modern technologies, and professional growth are part of everyday work. CUSTOMER Our Customer is a global SaaS company developing an AI-native revenue platform for modern finance and accounting teams. The company provides subscription management, billing automation, and revenue operations solutions that help organizations optimize financial workflows, improve scalability, and streamline transaction management across complex business ecosystems. Design, develop, and maintain scalable backend services and APIs for cloud-native applications Build and optimize distributed systems, payment processing pipelines, and backend infrastructure Ensure high availability, security, scalability, and performance of backend systems Participate in architecture discussions and contribute to technical strategy and decision-making Collaborate with Product, Frontend, AI, and DevOps teams to deliver high-quality solutions Mentor engineers through code reviews, technical guidance, and engineering best practices Troubleshoot complex production issues and drive continuous improvements Contribute to AI-powered product capabilities and AI/ML-driven initiatives Promote engineering excellence, observability, and maintainability across services and infrastructure 5+ years of professional Back-end software engineering experience using Python Solid experience designing and building RESTful APIs and distributed backend systems Strong knowledge of SQL and/or NoSQL databases Hands-on experience with AWS cloud services Experience with Docker and Kubernetes Understanding of scalable cloud-native architectures and microservices principles Experience working in cross-functional Agile teams Strong problem-solving, communication, and collaboration skills Ability to drive technical initiatives and contribute to architectural decisions Upper-Intermediate or higher English level WILL BE A PLUS Experience with FastAPI and TypeScript Experience building AI-powered user experiences or integrating AI/LLM services into Front-end applications Hands-on experience with AI technologies and LLM ecosystems Experience integrating OpenAI, Anthropic, or similar AI services Experience working with AI SDKs and prompt-based applications PERSONAL PROFILE Proactive and ownership-driven mindset Strong analytical and systems-thinking approach Ability to work effectively in a collaborative international environment