Expereo

Senior Backend Developer, Python

Expereo

full-time

Posted on:

Location Type: Hybrid

Location: Katowice • Poland

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Job Level

Senior

Tech Stack

AWSCloud.NETPython

About the role

  • We are looking for a Backend Developer to join the Supplier onboarding and Quote Management teams and work directly on the computational core of our platform.
  • You will write Python and/or dotnet every day. You will work on an existing Python/C# backend and create new services.
  • You will work on solving real-world business problems, like creating a constraint optimization engine, working on integrations with our partners and creating and maintaining internal tools.
  • Implement and maintain business logic for the quote engine, partner integrations and internal services: supplier selection, service bundling, routing rules, product validation …
  • Explore, document and integrate heterogeneous external data sources necessary to the execution of business logic.
  • Ensure all outputs are auditable, and explainable to commercial stakeholders — we don’t build black boxes.
  • Validate model outputs against historical data; measure and report on prediction reliability.
  • Optimize the operational value of the integrations with our partners.
  • Define contracts, manage versioning, and ensure downstream consumers are never broken silently.
  • Write clear, well-documented API interfaces with explicit input/output contracts and error handling.
  • Coordinate with the Platform engineer on service integration and ensure clean separation of concerns between components.
  • Maintain API documentation as a living artifact, not an afterthought.
  • Refactor and clean up existing Python/C# code: reduce complexity, increase testability, and bring the codebase up to production engineering standards.
  • Write unit and integration tests that provide real confidence — not just coverage numbers.
  • Apply Git, code review, and CI practices to all work. Code lives in a repository, goes through review, and is reproducible without intervention.
  • Document non-obvious logic thoroughly so knowledge is transferable.
  • Partner with the Commercial teams, Quote Engine lead Platform engineer — this is collaborative work, not ticket execution.
  • Participate in sprint reviews, propose approaches, and flag risks early.

Requirements

  • Advanced Python — non-negotiable. Clean, tested, reusable code. Not just scripts that happen to work.
  • API design and implementation. Designing and maintaining REST APIs with clear contracts, versioning, and proper error handling.
  • Software engineering discipline. Testing, code review, Git, and the habits of someone who builds things that others can maintain.
  • Ability to work in a mixed-language codebase. The existing platform is Python/C#. You need to be comfortable reading it and understanding the integration points.
  • C#: You will also work with the existing platform, you need to write quality, clean, testable code in C#.
  • Familiarity with AWS services (Lambda, API Gateway, S3) or equivalent cloud infrastructure.
  • Experience with API specification tooling (OpenAPI/Swagger, Pydantic, etc.).
  • Exposure to Python packaging, dependency management, and CI pipelines.
  • Familiarity with constraint-solving tools such as OR-Tools, PuLP, or equivalent in a real-world setting.
  • Experience in a B2B SaaS, telecom, or logistics context where algorithmic correctness has real commercial stakes.
  • Comfort with performance profiling and optimization in Python.
Benefits
  • Part of a team that is engaged and owning the things they do, highly trustable with direct commercial stakes.
  • Direct access to production systems, real data, and decision-makers — no layers of process between your work and its impact.
  • Exposure to cutting-edge technologies and large-scale global networks.
  • A role designed with trajectory in mind — the knowledge you build here is directly applicable to a senior technical execution path.
  • Competitive compensation
  • Pension Plan
  • Hybrid Working
  • 25 Days Holidays
Applicant Tracking System Keywords

Tip: use these terms in your resume and cover letter to boost ATS matches.

Hard Skills & Tools
PythonC#API designREST APIsunit testingintegration testingconstraint optimizationperformance profilingcode reviewsoftware engineering discipline
Soft Skills
collaborationproblem-solvingdocumentationcommunicationrisk management