Senior Python Developer - Build, Packaging & Migration

About the role

MAS Global Consulting, a digital engineering partner serving startups and large companies, is hiring a highly senior Python engineer to lead a migration from Python 3.7 / 3.9 to Python 3.12 across a large codebase of shared packages and their dependent services. The role takes end-to-end ownership of the packages and services assigned, planning the upgrade path, validating it and driving it to a safe rollout, with minimal direction.

Key responsibilities

• Own the migration of assigned packages and services: assess the dependency graph, define the upgrade path, implement it, validate it and drive it to a safe rollout.
• Prepare Python 3.12 migration and runtime-upgrade pull requests, following and helping evolve the team's migration plan.
• Resolve complex dependency and build compatibility issues: update version constraints, manage lock files and transitive dependencies, and replace deprecated or unmaintained libraries.
• Review and refine AI-generated migration changes (the team uses Claude Code heavily), deciding when to rely on automation and when to apply engineering judgment.
• Work on build scripts and the CI toolchain that validate upgrades, and improve migration scripts, build configuration, linting and static checks.
• Validate upgrades with unit, integration and runtime compatibility tests, investigate failures and document evidence for each change.
• Partner with package and service owners on code review, track progress and blockers, and escalate issues needing broader platform changes.

Required profile

• 7+ years of professional Python experience, including maintaining production services or shared libraries in a large codebase.
• Proven ownership of large-scale upgrades, such as Python runtime upgrades or dependency upgrades across many packages, or maintaining a core library used by multiple teams.
• Experience diagnosing behavior changes across Python versions and managing transitive dependencies.
• Daily use of AI coding agents such as Claude Code or Codex, with the judgment to critically review AI-generated code.
• Advanced English (B2/C1) is mandatory, with strong verbal and written communication skills.

Required skills

• Deep hands-on experience with modern Python packaging and dependency tooling, especially uv and/or Poetry, as well as pip, pip-tools, lock files, version constraints, virtual environments and package compatibility.
• Low-level Python and build system experience: how packages are built, resolved and installed, and how to debug failures at that level.
• Hands-on CI toolchain experience, building a CI pipeline from scratch or working inside an existing one, with linting, formatting and static analysis in CI/CD.
• Nice to have: Buildkite, large-scale refactors and staged rollouts, native Python extensions, Linux and Apple Silicon compatibility, reusable migration scripts, and a background in developer productivity, build and test infrastructure or platform engineering.