Company Description T‑Systems is part of the Deutsche Telekom Group, with around 30.000 employees worldwide. We are one integral team, guided by respect, integrity, and a passion for doing better every day. Our AI Foundation Services team builds the platform infrastructure that powers AI inference at scale, including API gateways, authentication, billing, and multi-tenant serving. designs and builds high-performance backend systems and APIs that power intelligent applications across diverse industries. We are looking for a senior backend engineer highly skilled Python Developer with strong system design skills and experience building production infrastructure deep experience designing, building, and scaling distributed systems and APIs. In this role, Y y You will ou will own architect and drive the evolution of the maintain backend platform behind our AI inference endpoints
- a multi-tenant system handling authentication, API key management, usage metering, billing and request proxy services that enable high-availability, data-intensive AI-powered solutions. The role is high-ownership and you will shape architecture decisions, raise the bar of engineering quality and build systems that are performant, secure and observable at scale. You’ll collaborate with experts in AI infrastructure and data engineering to build robust, secure, and efficient systems that scale to millions of requests. API gateway, authentication, authorization, key rotation, and multi-tenant isolation. Design, implement, and optimize APIs and backend systems using Python frameworks such as primarily FastAPI (or Flask, or Django). Architect and implement usage metering,



billing integration, and rate limiting for inference endpoints. Build and maintain scalable, fault-tolerant microservices for data processing and AI integration. Implement robust CI/CD pipelines, monitoring, and observability for high-performance production systems. Drive technical decisions on architecture, data modeling, and technology choices. Identify performance bottlenecks and drive improvements in reliability, scalability, and latency. Establish engineering standards for the backend codebase: testing, code review, CI/CD, and deployment practices. Degree in Computer Science, Software Engineering, or equivalent professional experience. ~5+ years of experience building and operating developing backend systems in production , with a meaningful scale with a focus on API design and high-scale production environments. ~ Strong proficiency in Python and at least one systems-oriented language (Go, Rust, Java, C++) , willingness to work across the current stack which includes Python (FastAPI)
- we value the right tool for the jobengineer with deep knowledge of asynchronous programming, modern Python tooling and profiling. ~ Solid understanding of distributed systems : consistency, fault tolerance, concurrency, performance and networking ,



data pipelines, and performance optimization. ~ Experience with cloud infrastructure (AWS, GCP, or Azure) and container s ized environments (Docker ) and orchestration ( , Kubernetes). ~ Understanding of database design (SQL, ORMs etc.) and data modeling at scale. ~ Fluent in English (written and verbal) and comfortable collaborating in international teams. integration of AI APIs, RAG workflows, or vector databases). Experience Knowledge of in modern DevOps practices, infrastructure as code, GitOps workflows and observability tools (Prometheus, Grafana, OpenTelemetry) . Exposure to ML serving infrastructure (model servers, GPU scheduling, inference optimization) is a plus but not required. Comfortable occasionally touching or contributing to frontend code when necessary. Experience in stress/load-testing and evaluating performance of production systems. Strong problem-solving mindset and commitment to code quality and performance excellence. Track record of improving engineering culture: mentoring junior engineers, introducing better practices, leading technical discussions. T-Social: social initiatives (sports, community, health, ...) Hybrid work model (remote/on-site) Flexible

working hours
Customized training: access to Coursera to learn whatever you want, whenever you want Weekly language classes (English, Spanish & German) Flexible compensation plan (health insurance, meal vouchers, childcare, transport) Social fund Free access to specialist services (medical, legal, wellness) ~Please send CV in English.

📌 Senior/ Lead Backend Engineer (España)
🏢 T-Systems Iberia
📍 España