Senior Backend Engineer – Python & AI

About the role

We are looking for a Senior Backend Engineer to join an AI Engineering team within a large international technology environment.

In this role, you will design, build, and operate robust Python backend services that power AI-enabled applications and reusable engineering capabilities across a complex enterprise ecosystem .

This is a highly hands-on senior individual contributor position, focused on solving real production challenges , making sound architectural decisions , and turning AI and data-science capabilities into secure, reliable, scalable, and maintainable software.

You will take ownership of backend services from initial design through production operation , working closely with Data Scientists, Product Managers, Platform Engineers, Security Specialists, and Architects .

If you enjoy building production-grade Python services , designing APIs and distributed systems , working with AWS , and integrating AI/LLM capabilities into real-world applications, this could be a great fit.

What you’ll do

Design, build, and maintain scalable backend services and APIs using Python

Own backend services end-to-end, from architecture and implementation through deployment and production operation

Integrate AI models , Large Language Models (LLMs) , and Machine Learning services into production systems

Define service boundaries , data models , persistence strategies , and integration contracts

Design resilient distributed systems with appropriate failure handling , retries , fallbacks , rate limits , and asynchronous processing

Work with relational databases , data modelling , schema evolution , and persistence strategies

Deploy and operate backend services in AWS cloud environments

Design services with reliability , security , observability , performance , and cost in mind

Handle production AI concerns such as latency , structured outputs , sensitive data , model failures , and external API limitations

Improve automated testing , CI/CD pipelines , monitoring , dashboards , logging , and alerting

Work with Docker and Kubernetes to containerise and operate backend workloads

Lead technical discussions, challenge weak architectural approaches , and help reduce unnecessary complexity





Participate in code reviews and help establish strong backend engineering standards

Mentor other engineers and share software engineering best practices

Collaborate closely with Data Scientists, Product Managers, Platform Engineers, Security Specialists, and Architects

Must Have

Typically 7+ years of experience in Backend Software Engineering , although technical depth , ownership , and impact are more important than an exact number of years

Strong Python software engineering skills

Solid experience designing and building backend services and REST APIs

Strong understanding of software architecture , service boundaries , distributed systems , and failure handling

Experience with relational databases , data modelling , and schema evolution

Hands-on experience deploying and operating production services in cloud environments , ideally AWS

Strong knowledge of software testing and engineering best practices

Experience with CI/CD pipelines and production deployment processes

Solid understanding of observability , logging , monitoring , dashboards , and alerting

Experience with Docker and Kubernetes

Practical understanding of security , privacy , sensitive data , and data protection principles

Strong problem-solving skills and ability to make and explain technical trade-offs

Experience working effectively across engineering, product, data, platform, and architecture teams

Fluent English and Spanish

✨ Nice to Have

Experience with FastAPI

Hands-on experience with AWS services and cloud-native architectures

Experience with Amazon EKS

Familiarity with Infrastructure as Code , especially Terraform

Experience with PostgreSQL , Amazon Aurora , or similar relational databases

Experience with asynchronous processing and event-driven architectures

Familiarity with queues , messaging systems , or event-based integration patterns

Experience with enterprise identity , authentication ,



and authorisation

Experience integrating AI , Machine Learning , or LLM capabilities into production backend systems

Familiarity with production concerns around LLM APIs , including latency , rate limits , retries , fallbacks , structured outputs , and observability

Experience in complex enterprise or large-scale digital environments

Hybrid model – 2 days onsite per week in Viladecans, Barcelona

Why join this project?

People first – diverse and inclusive culture in an international environment.

Build production-grade backend systems that power real AI-enabled applications

Work deeply with Python , APIs , distributed systems , databases , and cloud-native technologies

Gain exposure to real-world AI and LLM integration without moving away from hands-on software engineering

☁️ Work in an AWS-based environment with modern cloud and platform engineering practices

⚙️ Influence architecture , engineering standards , reliability , observability , and production quality

Take real ownership of services and technical decisions instead of simply implementing predefined tickets

Remain hands-on while having meaningful technical influence across the team

High team stability and collaborative culture.

€1200 per year training budget and continuous learning opportunities.

Versátil compensation model .

Private health insurance and benefits package.

⚡ Flexible working hours and hybrid model .

️ Wellhub : fitness, wellness, and mental health support.

⚽ Football and paddle tennis teams sponsored by Capitole .

Team buildings, global events, and strong tech communities .

Want to know more about us? Click here and discover all the details.

Curious about our culture? Check out what people are saying about us on Glassdoor .

We know that not every candidate will meet 100% of the requirements. If your profile doesn’t match perfectly but you believe you can add value, we’d still love to hear from you.

Ready for the challenge? Apply now!

Empowering People, Unlocking Innovation.

Information Security Notice

The employee will have access to confidential information related to Capitole and the assigned project.

Compliance with internal security and information protection policies is mandatory.

📌 Senior Python Backend Engineer (Barcelona)
🏢 Capitole
📍 Barcelona