Senior Backend Software Engineer

Flexcompute-Inc.; Comunidad de Madrid; On-site; EUR 85,000 - 125,000; Full time

Benefits offered by this job

Remote within Spain

Flexible hours

Unlimited PTO

Travel to Boston

Learning sponsorship

AI tools budget

Job summary

Flexcompute is seeking a Senior Backend Software Engineer to design and deploy scalable solutions for our EM simulation platform, Flow360 and Tidy3D. You will own backend services end-to-end, contribute to API unification, data management, and cloud integration, while coordinating with EM and infra teams.

The role emphasizes production ownership, distributed systems, and a strong backend stack (Java/Python/C++), with AWS experience and Spanish work rights.

Qualifications

• Strong backend engineering in at least one of Java, Python or C++.
• Production cloud experience, AWS preferred.
• Distributed systems you have operated in production.
• Direct ownership of a production backend service from design to operation.
• Fluent professional English, spoken and written.
• Based in Spain with right to work there without visa sponsorship.

Responsibilities

• Contribute to API unification, data management, and scripting improvements.
• Collaborate with EM and infra teams to enhance back-end/scheduler integrations.
• Improve web API design for a multi-physical simulation context.
• Develop and maintain hybrid cloud compute and storage solutions.
• Optimize and manage HPC clusters and high-speed interconnects.

Skills

Backend engineering

Java

Python

C++

AWS cloud

Distributed systems

Production ownership

English proficiency

Spain work rights

Education

Bachelor's in CS or related

Tools

Docker

Kubernetes

Job description

Flexcompute is leading the transformation of engineering simulation with our revolutionary ultra-fast simulation technology. Our flagship products, including the industry-leading Computational Fluid Dynamics (CFD) software Flow360 and electromagnetic simulation software Tidy3D, are reshaping how simulations are conducted across diverse sectors. Founded by visionaries from Stanford and MIT and supported by top-tier venture capital firms, we are a rapidly growing team dedicated to breaking boundaries and challenging the norms of the multi-billion-dollar engineering simulation market.

Role Overview

We are looking for a Senior Backend Software Engineer to help us design and implement scalable solutions that meet the growing demands of our advanced EM simulation platform.

Additionally, the candidate will help us enhance our data management, frontend-backend API unification, and cloud integration.

Key Responsibilities

• Contribute to general software development efforts, such as API unification, simulation data management (e.g., caching, syncing, storage), and scripting improvements.
• Collaborate with EM and infrastructure teams to implement simulation-specific solutions, including enhancements to back-end/scheduler integrations and Python front-end functionality.
• Improve our task pipelines through an innovative design for a web API in a multi-physical simulation context.
• Develop and maintain hybrid cloud compute and storage solutions, integrating on-premise HPC systems with modern cloud platforms.
• Optimize and manage high-performance computing clusters equipped with high-speed interconnects

This is a senior seat. We keep the team small and senior on purpose, so you will own real pieces of the platform end to end, with little direction and direct access to the founders.

What you need

• Strong backend engineering in at least one of Java, Python or C++. Deep in one is enough.
• Real production cloud experience, AWS preferred.
• Distributed systems you have operated in production, not only studied.
• Direct ownership of a production backend service, from design through deployment and operation.
• Fluent professional English, spoken and written.
• Based in Spain, with the right to work there without visa sponsorship, and available on Spanish working hours with about six hours of overlap with our Boston team.
• A bachelor's degree in computer science, computer engineering, telecommunications engineering or a closely related field.

What you can learn here

We hire for depth, not checklists. You do not need all of the following on day one: Kubernetes and Docker, Terraform or Ansible, monitoring and observability tooling, Linux troubleshooting, networking and security practices, our simulation stack, and HPC (preferred, not mandatory). We look for people who have entered a new domain before, learned it fast and reached ownership.

Bonus

• Load balancing, autoscaling, and queues or streaming systems such as SQS, SNS or Kafka.
• Experience integrating cloud platforms with HPC environments or large compute clusters.
• Familiarity with job schedulers or batch systems, distributed compute frameworks, or large-scale data pipelines.
• Experience supporting scientific computing or simulation platforms.
• Knowledge of GPU infrastructure and resource scheduling.
• Experience building developer platforms or internal infrastructure tooling.
• A degree in computer science, computer or telecommunications engineering, mathematics, physics or a related field from a leading university. Hands-on production experience matters more than where you studied.

Innovative Mindset

Ability to learn quickly, adapt to new challenges, and innovate in a fast-paced startup environment.

Example Projects

• Architect and deploy infrastructure that runs distributed simulation workloads across cloud and on-premise compute
• Design and implement scalable web APIs for simulation job orchestration and data access
• Build CI/CD pipelines and infrastructure-as-code systems for reproducible deployments
• Develop hybrid cloud solutions connecting on-prem HPC clusters with AWS compute and storage
• Implement monitoring and observability systems to track simulation performance and reliability
• Improve platform scalability to support growing user traffic and compute demand
• Design secure service architectures, authentication, and licensing systems
• Optimize infrastructure utilization across CPU and GPU resources

Join Us

By joining Flexcompute, you'll be at the heart of a movement set to redefine the engineering simulation industry. You will play a key role in shaping the future, where our innovations in simulation technology pave the way for groundbreaking advancements. We are committed to fostering an innovative and collaborative culture where boundaries of possibility are re-imagined, driven by creativity, expertise, and a shared vision of transforming the technological landscape.

How we hire

No online assessment. Two to three technical conversations with the engineering team, then a final conversation with a co-founder. Bring your questions: the first conversation is not a pitch you sit through, you are welcome to send questions ahead, and technical disagreement is welcome.

• Competitive compensation and equity.
• Remote within Spain, on Spanish working hours with about six hours of overlap with our Boston team.
• Fully flexible hours and unlimited PTO.
• Periodic company-paid travel to Boston to work with the core team.
• Learning sponsorship, a travel allowance, an AI tools budget (we pay for Claude, Cursor and similar) and a fitness benefit.
• Friendly, thoughtful, and intelligent coworkers.