Strong Middle / Senior Full Stack Developer (TypeScript / React)

Sigmasoftware2; Warszawa; On-site; PLN 180,000 - 240,000; Full time

Job summary

Sigmasoftware2 in Warszawa, Poland is seeking a senior full stack developer to design, build, and maintain scalable applications using JavaScript/TypeScript, NestJS, and React. You will contribute to architecture decisions and work across product teams.

The role emphasizes delivering high-load systems, cloud exposure with AWS, and a strong culture of code quality, testing, and continuous improvement. English communication required; Polish language helpful.

Qualifications

• 4-5+ years of commercial JS/TS development with backend focus.
• Strong NestJS backend experience.
• Solid ReactJS frontend experience.
• Hands-on AWS cloud experience.
• Understanding of scalable system architecture and best practices.
• Experience with enterprise-level or high-load applications.
• Strong problem-solving and analytical skills.
• Ability to work independently and own technical solutions.
• Good communication and collaboration skills.
• Upper-Intermediate or higher English level.

Responsibilities

• Design, develop, and maintain scalable Full Stack applications using JavaScript, TypeScript, NestJS, and React
• Implement and support complex business logic related to digital advertising campaign management
• Participate in technical discussions, architecture decisions, and solution design activities
• Collaborate closely with developers, Architects, QA engineers, and Project Managers
• Improve application performance, scalability, reliability, and maintainability
• Develop clean, maintainable, and well-tested code following software engineering best practices
• Identify technical challenges proactively and drive solutions independently
• Contribute to continuous improvements in development processes and technical standards

Skills

Back-end development

NestJS

Front-end development

ReactJS

AWS

System architecture

High-load systems

Problem solving

English proficiency

AI-native development

Tools

Jenkins

Terraform

Job description

Responsibilities

• Design, develop, and maintain scalable Full Stack applications using JavaScript, TypeScript, NestJS, and React
• Implement and support complex business logic related to digital advertising campaign management
• Participate in technical discussions, architecture decisions, and solution design activities
• Collaborate closely with developers, Architects, QA engineers, and Project Managers
• Improve application performance, scalability, reliability, and maintainability
• Develop clean, maintainable, and well-tested code following software engineering best practices
• Identify technical challenges proactively and drive solutions independently
• Contribute to continuous improvements in development processes and technical standards

Qualifications

• 4-5+ years of commercial software development experience with JavaScript and TypeScript, with a primary focus on back-end development
• Strong Back-end development experience with NestJS
• Solid Front-end development experience with ReactJS
• Hands-on experience with AWS cloud services
• Good understanding of scalable system architecture and software engineering best practices
• Experience working with enterprise-level or high-load applications
• Strong problem-solving and analytical skills
• Ability to work independently and take ownership of technical solutions
• Good communication and collaboration skills
• Upper-Intermediate or higher English level
• WILL BE A PLUS
• AI-native development experience
• Familiarity with AI-powered development tools such as Claude and Codex
• Experience with Jenkins
• Experience with Terraform
• Experience working with complex or enterprise platforms

Personal Profile

• Proactive and self-driven mindset
• Strong ownership attitude
• Team-oriented and collaborative approach
• Ability to work effectively in a fast-paced engineering environment
• Strong attention to code quality and technical excellence