Senior Full-Stack Engineer: Modernization & Migration Remote

Looi Consulting LLC.; Polska; Hybrid; PLN 240,000 - 360,000; Full time

Job summary

Jobsoid Inc. is seeking a Senior Full-Stack Engineer to lead the transition of a mature SaaS app from legacy Microsoft tech to React and Node.js.

You will own design, migration planning, and delivery across UI, APIs, services, and data with an emphasis on data integrity and test coverage. Remote work is offered; ideal candidates will have modernized live applications, strong REST API design skills, and experience with AI-assisted coding tools.

Qualifications

• 7+ years of professional software development experience with full-stack focus.
• Strong React and TypeScript in production apps.
• Backend experience with Node.js and TypeScript.
• Designed REST APIs, service layers, and data-access components.
• Strong SQL and relational DB expertise.
• Experience modernizing live production systems.
• Knowledge of migration approaches minimizing downtime.
• Strong automated testing across unit and integration.
• Experience with Git, PRs, and CI/CD workflows.
• Experience using AI coding assistants in development.
• Ability to document requirements and architecture.
• Ownership from discovery to production validation.
• Strong written communication and collaboration.

Responsibilities

• Design and develop full-stack functionality using React, Node.js, and TypeScript.
• Shape target architecture, project organization, conventions, testing strategy, and delivery practices.
• Migrate complex workflows from legacy to modern stack.
• Build maintainable REST APIs and data-access components.
• Divide migration work into testable, deployable increments.
• Ensure legacy and modern components operate safely together.
• Analyze code and workflows to preserve business rules and data relationships.
• Write secure, parameterized SQL queries and optimize DB interactions.
• Develop unit, integration, and end-to-end tests.
• Produce modular, well-documented code and focused PRs.
• Apply migration safeguards including staged releases and rollback planning.
• Use AI-assisted tools to support coding and testing.
• Evaluate AI-generated code for correctness and security.
• Collaborate with leadership through documentation and reviews.
• Investigate and resolve deployment and validation issues.
• Establish sustainable engineering patterns for the team.

Skills

React

TypeScript

Node.js

REST APIs

SQL

Automated testing

Git

CI/CD

AI coding assistants

Code reviews

Tools

Playwright

AWS

SQL Server

CI/CD tooling

Job description

Jobsoid Inc. is seeking a Senior Full-Stack Engineer to lead the transition of a mature SaaS app from legacy Microsoft tech to React and Node.js.

You will own design, migration planning, and delivery across UI, APIs, services, and data with an emphasis on data integrity and test coverage. Remote work is offered; ideal candidates will have modernized live applications, strong REST API design skills, and experience with AI-assisted coding tools.