Principal Engineer: Backend Architecture & Modernization

ABC Fitness; Poland; On-site; PLN 460,000 - 470,000; Full time

Benefits offered by this job

Competitive compensation package

Medical/Dental/Vision coverage

Flexible benefits & PTO

Job summary

ABC Fitness seeks a Principal Engineer to lead the modernization of critical software systems while remaining hands-on across architecture, APIs, data access, and deployment. You will guide domain modeling, service boundaries, and evolution of legacy applications into well-structured software.

This is a hands-on, principal-level leadership role focused on durable software and business continuity. You will drive correctness, performance, and reliability, mentor teams through architectural

Qualifications

• Deep backend and distributed-systems engineering experience.
• Able to move from architecture into code, configuration, instrumentation, and diagnosis.
• Strong testing, code review, and production validation practices.

Responsibilities

• Lead software architecture and modernization.
• Shape evolution of legacy applications into domain-oriented software.
• Stay hands-on in code and contribute to critical implementations and reviews.
• Design clear domain models, APIs, and service contracts.
• Modernize application foundations and upgrade frameworks and runtimes.
• Engineer for correctness, performance, and reliability.
• Improve data access, persistence, and messaging patterns.
• Establish reusable engineering patterns and cross-team execution.

Skills

Backend engineering

Distributed systems

Code implementation depth

Architecture judgment

Production reliability

Testing discipline

AI-assisted engineering

Tools

Java/Springboot

Golang

Node/TypeScript

Job description

ABC Fitness seeks a Principal Engineer to lead the modernization of critical software systems while remaining hands-on across architecture, APIs, data access, and deployment. You will guide domain modeling, service boundaries, and evolution of legacy applications into well-structured software.

This is a hands-on, principal-level leadership role focused on durable software and business continuity. You will drive correctness, performance, and reliability, mentor teams through architectural