Senior Python Engineer

Senior Python Engineer – Platform Migration

Location: Wrocław, Poland (preferred) | Hybrid

Type: Contract (B2B) - Higher end of market rate

Company: Leading Investment Bank

Role Overview

This is a senior Python engineering role focused on refactoring, stabilising and maintaining backend services and APIs during a major platform migration. The engineer will ensure that existing Python services continue to operate reliably as the organisation transitions from a Spark/Cassandra environment to Databricks with Delta tables.

Key Responsibilities

Backend Engineering & API Development

• Develop, refactor and maintain Python backend services and APIs.
• Work with FastAPI or Flask to build and support production‑grade services.
• Update services to retrieve data, trigger model execution, and publish results.

Migration & Refactoring

• Repoint services from Cassandra to Delta tables.
• Ensure behaviour, outputs and performance remain consistent pre‑ and post‑migration.
• Apply strong engineering discipline around testing, validation and reliability.

Performance, Testing & Stability

• Implement regression testing and validation strategies.
• Diagnose and prevent performance issues in backend services.
• Ensure services remain stable during platform changes.

Collaboration

• Work closely with data platform teams, quants and data science users (without owning modelling work).
• Contribute to a high‑quality engineering culture focused on reliability and production readiness.

Technical Environment

Python Stack

• Strong commercial Python experience (5+ years).
• FastAPI and/or Flask.
• Pandas, NumPy.
• Python packaging and dependency management.

Platform & DevOps

• Working knowledge of Azure.
• CI/CD systems (GitLab CI, Jenkins or similar).
• Containers (Docker; Kubernetes familiarity beneficial).
• Git‑based version control.

Data & Services

• Practical SQL knowledge.
• Understanding of backend performance and service reliability.
• Experience refactoring systems due to backend or platform changes.

Must‑Have Skills

• 5+ years of Python engineering experience.
• Proven experience building and maintaining production APIs/services.
• Strong FastAPI/Flask experience.
• Experience refactoring or migrating existing systems.
• Strong testing mindset (regression, validation, reliability).
• Cloud‑hosted environment experience (Azure preferred).
• Practical SQL skills.
• Solid understanding of backend performance and service stability.

Nice‑to‑Have Skills

• Docker and Kubernetes.
• Exposure to Azure ML or AI services (integration level).
• Experience with analytics‑heavy services.
• React/UI exposure (useful but not required).