Senior Backend & AI Engineer (all identities)

OpenKrill; United States; Remote; USD 88,000 - 99,000; Full time

Benefits offered by this job

Home office allowance

Meal subsidy

30 vacation days per year

Learning & development budget

Ownership and autonomy

Collaborative culture

Well-being programs

Snacks and drinks

Job summary

Caspar Health is building an agile backend squad to own end-to-end features, from design to production. You will develop Ruby on Rails services, robust APIs, and data models while implementing LLM workflows with quality checks.

The role requires senior backend experience, strong API design, and the ability to work autonomously with product and domain experts in a remote-first environment in Germany.

Qualifications

• Senior experience building and maintaining complex systems using Ruby on Rails.
• Strong API design skills and data model experience.
• Solid understanding of system architecture including authorization and billing workflows.
• Practical experience building LLM applications and agent workflows.
• Ability to own features from design to live production.
• Clear technical communication with product and domain experts.

Responsibilities

• Own end-to-end feature development including implementation, testing, release, and operations.
• Develop scalable Ruby on Rails services and robust APIs.
• Design data models and manage background jobs such as authorization and billing workflows.
• Build and optimize LLM workflows and agent applications with quality checks.
• Collaborate closely with Product Manager and domain experts.
• Participate in technical reviews and establish engineering standards.

Skills

Backend Engineering

API Design

System Architecture

LLM Practice

End-to-End Ownership

Technical Communication

Tools

Ruby on Rails

Job description

What to Expect

Build intelligent backend systems that make a genuine impact in healthcare. Caspar Health is the leading digital platform for medical rehabilitation. We empower doctors, therapists, and nursing staff to care for patients as quickly, effectively, and sustainably as possible. To take our platform to the next level, we are expanding our small, highly agile backend squad (consisting of 3 engineers and a Product Manager). In this role, you will take full technological ownership: from designing robust Ruby on Rails services and clean API architectures to building LLM-based agent workflows with repeatable quality checks. If you are passionate about combining modern AI engineering with true purpose and highest software standards, you will thrive here.

We appreciate your expertise and wish to provide full transparency regarding the compensation range for this role. Your starting salary will be aligned with your qualifications, relevant experience, skill set, and market benchmarks. Remuneration for this position follows our internal salary bands and ranges from €78,000 to €88,000 gross annually (based on a full-time 40-hour work week). This role is located in Germany and requires full physical presence within the country. Due to our existing payroll and social security framework, permanent remote employment from abroad is not supported. Candidates must be eligible to work in Germany and resident from their first day. Please be advised that we cannot offer visa sponsorship or relocation assistance at this time.

Your Challenges

• System Architecture: Full end-to-end ownership of your features across implementation, automated testing, release, and live operation.
• Backend Engineering: Development of scalable Ruby on Rails services, robust APIs, data models, and background jobs including authorization and billing workflows.
• LLM Workflows: Building and optimizing LLM applications, evaluation pipelines, and agent workflows with repeatable quality checks.
• Product Collaboration: Close partnership with Product Manager and domain experts to turn complex requirements into maintainable, high-performance software.
• Technical Reviews: Active contribution through clear technical reviews, operational monitoring, and explicit technical decision-making.
• Quality Standards: Shaping our shared delivery practices and establishing modern test and engineering standards across the team.

Your Profile

• Backend Engineering: Strong senior experience in building and maintaining complex systems using Ruby on Rails.
• API Design: Proven expertise in designing clean APIs, data models, and managing background job processing.
• System Architecture: Sound understanding of authorization concepts, billing workflows, and automated testing strategies.
• LLM Practice: Practical experience building LLM applications, evaluations, and agent workflows.
• End-to-End Ownership: Ability and mindset to own functionality independently from initial design to live production.
• Technical Communication: Strong communication skills to collaborate with product and domain experts and make technical trade-offs explicit.

Why Caspar Health?

• Remote-first with flexible working hours - office optional in Berlin-Mitte or up to 90 days a year outside of Germany
• To match this, we support you with a monthly home office allowance and an additional meal subsidy.
• Plenty of time to recharge - with 30 vacation days per year.
• Budget for learning & development, conferences, and coaching - tailored to your potential and growth opportunities.
• High level of ownership and decision-making freedom - no micromanagement. We hire experts who know what they’re doing. #MakeAnImpact!
• Genuine collaboration - no silos, no egos. After all, we’re all working toward the same vision. #ValueFocus!
• Access to all Caspar offerings for mental and physical well-being #HealthyTogether!
• And yes – all the snacks your heart desires, group sports sessions, a never-empty drinks fridge, and a healthy dose of humor are included too.

What defines us as a team

• We live diversity - it's not a marketing slogan, it's part of our everyday reality.
• Feedback isn’t a tool - it’s part of our culture.
• We believe that technology only makes sense when it truly helps people.
• Our drive is purpose - but our standard is professionalism.

Diversity and Inclusion

At Caspar Health, we strive to provide a friendly, safe and welcoming environment for all Casparians* regardless of ethnic origin, gender, gender identity and expression, sexual orientation, limitations of any kind, physical appearance, social background, age or religion (or lack thereof).

When you apply, we purely focus on your experience and motivation. You decide what additional information you want to disclose (picture, marital status, religion, gender, nationality, etc). We value and treat all applications equally.

We are looking forward to getting to know you!

Your Contact

Hannah Christiani, Talent Acquisition Specialist

[e-mail]