Company Description
T?Systems is part of the Deutsche Telekom Group, with around ** employees worldwide. We create technology with purpose to generate a positive impact on society. We are looking for curious talent, eager to learn, take on challenges, and contribute ideas that transform our customers' experience.
We trust people: we offer autonomy, continuous support, and a collaborative environment where you can grow without limits. We are one integral team, guided by respect, integrity, and a passion for doing better every day.
Job Description
T-Systems is at the forefront of innovation, delivering advanced technology solutions across sectors including automotive, healthcare, and public services. 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 cultivate a collaborative engineering culture where
technical depth
creativity and
ownership
technical expertise drive real-world impact.
Role Overview
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.
Responsibilities and Duties
Design and build core platform services: 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.
Build and operate a high-throughput proxy/routing layer for AI model serving traffic.
Collaborate with cross-functional teams to design system architecture and ensure seamless system interoperability.
Design telemetry and observability into the platform from the ground up — structured logging, distributed tracing, metrics, and alerting.
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.
Ensure best practices for security, compliance, and maintainability across the API lifecycle.
Collaborate closely with the ML infrastructure team to integrate with model serving systems (e.g., NVIDIA Dynamo, vLLM, SGlang, TensorRT-LLM).
Qualifications
Must-have requirements:
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.
Proven experience designing and maintaining REST APIs (
REST, gRPC, WebSockets, SSE
Including websockets, SSE, Webhooks etc.) in production environments
and the tradeoffs between them
.
Solid understanding of distributed systems
: consistency, fault tolerance, concurrency, performance and networking
, data pipelines, and performance optimization.
Experience designing authentication/authorization systems (OAuth2, JWT, API key management, RBAC/ABAC).
Experience with cloud infrastructure (AWS, GCP, or Azure) and

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