Senior AI Developer

Billennium; Poland; Hybrid; PLN 180,000 - 240,000; Full time

Benefits offered by this job

Udemy for Business

Private medical care

Multisport card

Veterinary package

Language lessons

Shopping vouchers

Remote/hybrid work options

Career growth opportunities

Team-building events

Annual Mazury company event

Welcome pack

Job summary

Billennium, a global technology company, is seeking an experienced Senior Developer with strong Python, cloud-native development and AI/LLM expertise. You will contribute to building production-grade intelligent solutions used by enterprise clients worldwide.

In this role you will design and implement scalable FastAPI services, develop end-to-end LLM-powered features, and optimize AI workflows, latency and costs while collaborating with a diverse, international team.

Qualifications

• Solid understanding of software architecture, design patterns and API development.
• Hands-on experience with LLM APIs and AI-driven applications.
• Good understanding of RAG, prompt engineering and LLM evaluation.
• Experience with LangGraph or similar agentic AI frameworks.
• Experience with FastAPI or similar Python frameworks.
• Strong knowledge of Azure, Docker and Kubernetes.
• Familiarity with CI/CD and IaC tools like Terraform, Bicep or ARM.
• Experience with monitoring/observability tools (App Insights, Prometheus, Grafana).
• Proven scalability, performance optimization and production troubleshooting.
• Experience with code reviews, mentoring and establishing engineering standards.
• Fluent English and strong communication skills.

Responsibilities

• Build LLM-powered features end to end.
• Design and implement agentic workflows, RAG and tool calling using LangGraph.
• Develop scalable FastAPI services with streaming, persistence and automated tests.
• Build evaluation datasets, regression suites and LLM-as-a-judge solutions to measure and improve answer quality.
• Design effective retrieval strategies and orchestrate multi-step research workflows.
• Investigate AI-related issues and identify root causes (retrieval, prompting, model).
• Instrument and debug production AI workflows using Langfuse and tracing.
• Optimize latency, token usage and AI costs, including model routing via AI gateway.
• Build and optimize scalable backend systems in Azure.

Skills

Software architecture

API development

LLM APIs

RAG

Prompt engineering

LangGraph

FastAPI

Python

Azure

Docker

Kubernetes

CI/CD

Infrastructure as Code

Observability tools

English communication

Tools

Azure

Docker

Kubernetes

Terraform

Bicep

ARM

Application Insights

Prometheus

Grafana

Job description

Billennium is a global technology company delivering innovative software, cloud, data and AI solutions for enterprise clients worldwide. We combine engineering excellence with a collaborative culture to help organizations accelerate their digital transformation.

We are looking for an experienced Senior Developer with strong expertise in Python, cloud-native development and AI/LLM technologies.

Why Billennium?

You’ll work in a technology-driven environment where software engineering, cloud and AI come together. You’ll have the opportunity to work with modern technologies and contribute to building production-grade intelligent solutions used in real-world business scenarios.

What will you do?

• Build LLM-powered features end to end
• Design and implement agentic workflows, RAG and tool calling using LangGraph
• Develop scalable FastAPI services with streaming, persistence and automated tests
• Build evaluation datasets, regression suites and LLM-as-a-judge solutions to measure and improve answer quality
• Design effective retrieval strategies and orchestrate multi-step research workflows
• Investigate AI-related issues and identify whether the root cause is retrieval, query formulation, prompting or the model
• Instrument and debug production AI workflows using Langfuse and tracing
• Optimize latency, token usage and AI costs, including model routing through an AI gateway
• Build and optimize scalable backend systems in Azure

What are we looking for?

• Solid understanding of software architecture, design patterns and API development
• Hands-on experience with LLM APIs and AI-driven application
• Good understanding of RAG, prompt engineering and LLM evaluation
• Experience with LangGraph or similar agentic AI frameworks
• Experience with FastAPI or similar Python frameworks
• Strong knowledge of Azure, Docker and Kubernetes
• Familiarity with CI/CD and Infrastructure as Code tools such as Terraform, Bicep or ARM
• Experience with monitoring and observability tools such as Application Insights, Prometheus, Grafana or similar
• Proven experience in scalability, performance optimization and production troubleshooting
• Experience with code reviews, mentoring and establishing engineering standards
• Fluent English and strong communication skills

Perks and benefits:

• Comprehensive benefits-enjoy Udemy for Business, private medical care, Multisport card, veterinary package, language lessons, and shopping vouchers.
• Flexibility-adaptable working hours and remote/hybrid work options to suit your lifestyle & location.
• Career growth-access to professional development and learning opportunities, including perks from our official partnerships with global IT giants: Microsoft, AWS, Snowflake, Salesforce & more.
• Global collaboration-work with a diverse, international team.
• Innovative environment-be part of a forward-thinking and growth-oriented workplace.
• Engaging community-participate in team-building events, hackathons, and CSR initiatives to make an impact beyond work.
• Team-building events, including our company tradition-an annual company event in Mazury.
• A welcome pack to start your journey with us on a positive note.

Recruitment process

• HR call
• Interview with the dedicated Client