Back-End Tech Lead

For our client - a fast-growing AI-driven fitness and wellness product - we are looking for a Backend Tech Lead to take technical ownership of the backend platform as it evolves from a consumer-focused product into a system capable of reliably supporting large-scale partnerships and step-function growth.

A significant part of the product is built around AI capabilities, including LLM-powered agents and computer vision. The backend plays a central role in orchestrating these components: integrating models, managing data flows, and scaling AI-backed features in production.

This role is for a senior, hands-on backend engineer with strong architectural judgment. You will work on a production system in Python, help scale it for high load and reliability, and shape how backend services are designed, built, and operated going forward. The role carries high technical and process authority and is deeply involved in delivery. People management is not required, but experience leading teams or squads is welcome.

• Take ownership of the current backend architecture (Python distributed monolith + services)

• Design and operate backend services that integrate with LLMs and bespoke ML systems

• Evolve the system to handle high load, burst traffic, and partner-driven scale

• Design pragmatic, incremental improvements balancing speed, reliability, and long-term maintainability

• Write production code on critical backend paths on a weekly basis

• Deliver both product features and technical improvements from early stages

• Own changes end-to-end: system design, implementation, rollout, and monitoring

• Design and optimize systems for performance, throughput, and resilience

• Work with relational databases (PostgreSQL preferred): schema design, query optimization, migrations, replication, and bottleneck analysis

• Own and improve APIs between backend services, mobile applications, and AI components

• Establish clear, stable, and scalable contracts aligned with product and partner needs

• Help define how backend responsibilities are split across services as the system grows

• Raise the bar on logging, metrics, tracing, alerting, and operational visibility

• Collaborate closely with SREs and engineers on reliability and incident response

• Design systems with failure modes and recovery strategies in mind

• Lead architectural discussions for new features and major system changes

• Influence engineering practices: code reviews, PR flow, delivery discipline, and technical decision-making

• Act as a reference point for backend decisions without becoming a bottleneck

Must-have experience

• Strong backend engineering experience with Python (Django and/or FastAPI)

• Proven experience scaling backend systems for performance, reliability, and high load

• Deep experience with relational databases (PostgreSQL preferred)

• Hands-on experience with message-based systems (e.g. RabbitMQ or similar)

• Experience running backend systems on cloud infrastructure (AWS or equivalent)

• Strong understanding of API design for backend ↔ mobile client interactions

• Clear delivery mindset: you ship, iterate, and take ownership of outcomes

• Strong architectural judgment and ability to work within real-world constraints

• Fluent English

Nice to have

• Experience with other languages such as Go

• Experience designing systems for large partners or enterprise-scale usage

• Experience with CI/CD pipelines and production operations

• Experience working in fast-moving or ambiguous environments

• Interest in health, fitness, or consumer-facing products

• Work on a fast-growing AI-driven fitness and lifestyle product

• AI and LLMs are core not only to the product, but also to day-to-day engineering work

• Direct impact on product direction and architectural decisions

• Unique intersection of B2C scale and large B2B partnerships

• Growth comes from tackling complex technical challenges, deep ownership, and broad influence

• Small, people-oriented team with a strong engineering culture

Dear Candidates, due to a high volume of applications, only selected candidates will be contacted for interviews. We appreciate your understanding. Thank you for considering a career with us!

• Work type
• Full-time
• Location
• Warsaw