Middle Full-Stack Software Engineer (React + .NET)

Symphony Solutions; Poland; On-site; PLN 120,000 - 180,000; Full time

Job summary

Symphony Solutions is seeking a Full-Stack Software Engineer (React + .NET) to join our Development Team in Poland. You will work across back-end and front-end, modernizing existing applications and taking ownership of features, with emphasis on clean, maintainable code and pragmatic problem-solving.

Ideal candidates have 3+ years in .NET, strong REST API experience, and solid React + TypeScript skills. You will collaborate with UX, product, QA, and operations to deliver reliable, scalable

Qualifications

• 3+ years of .NET and application development experience.
• REST APIs with ASP.NET Core, .NET Core / .NET MVC, and C#.
• Modern web stack: HTML5, SCSS, TypeScript, React, Redux.
• EF Core, SQL Server, and LINQ.
• CI/CD and source control (Git).
• English at B2 level.
• Experience with AI features or tools integration.
• Familiarity with Azure DevOps, Jenkins, or Octopus.

Responsibilities

• Design, develop, test, and maintain applications using C#, .NET Framework/.NET Core, and modern .NET.
• Modernize legacy .NET architectures and improve existing applications.
• Develop RESTful APIs and microservices, ensure secure authentication and logging.
• Collaborate with cross-functional teams in Agile/Scrum workflows.
• Review code and contribute to engineering standards.
• Ensure clean, maintainable, and testable code with good architecture.
• Work on front-end with React + TypeScript as part of full-stack delivery.
• Participate in CI/CD daily operations and DevOps practices.

Skills

3+ years in .NET

REST APIs with ASP.NET Core

React + TypeScript

EF Core

Git

CI/CD

Azure DevOps / Jenkins / Octopus

English B2

AI integration experience

Tools

Git

Azure DevOps

Jenkins

Octopus

Job description

What is the project, and why should you care?

Our client is a global customer strategy and insights company that helps leading brands better understand their customers and turn those insights into meaningful business decisions. Combining technology, research, data, and human-centered design, the company creates digital solutions that enable organizations to engage with customers, gather valuable feedback, and continuously improve their products and services.

The Development Team plays a key role in building, maintaining, and continuously improving these digital products and platforms. Working in a collaborative, cross-functional environment alongside UX specialists, product experts, researchers, and data professionals, the team develops reliable, scalable, and intuitive solutions while tackling complex technical challenges.

We are currently looking for a Full-Stack Software Engineer (React + .NET) to join the Development Team. In this role, you will work across both back-end and front-end development, contributing to existing applications as well as their ongoing modernization. You will have the opportunity to take ownership of your work, contribute to technical and architectural decisions, participate in code reviews, and collaborate with colleagues across development, design, QA, and operations.

We are looking for an engineer who values clean, maintainable code, pragmatic problem-solving, knowledge sharing, and continuous improvement, and who is comfortable working with both established systems and modern technologies.

You will be an excellent fit for this position if you have:

Required

• 3+ years of .NET and application development experience.
• Experience building REST APIs with ASP.NET Core, .NET Core / .NET MVC, and C#.
• Familiarity with modern web development: HTML5, SCSS, TypeScript, React, and Redux.
• Experience with Entity Framework.
• Experience with source control systems (Git preferred).
• Understanding of DevOps and CI/CD processes.
• Familiarity with technical design, architecture, best practices, and patterns.
• English proficiency at B2 level.
• Experience working with AI technologies, including integrating AI features or tools into applications.
• Experience with Azure DevOps, Jenkins, or Octopus.

Here are some of the things you'll be working on:

• Design, develop, test, and maintain applications using C#, .NET Framework, and modern .NET (.NET Core / .NET 6+).
• Work effectively with legacy .NET applications, understanding existing architecture and identifying opportunities for incremental modernization.
• Refactor and modernize legacy functionality without unnecessarily introducing risk to existing applications.
• Understand the differences between traditional monolithic .NET architectures and modern distributed/cloud-based architectures.
• Develop clean, maintainable, testable, and reusable code.
• Participate in code reviews and contribute to engineering standards and best practices.
• Design and develop RESTful APIs and microservice-based solutions using modern .NET technologies.
• Understand API contracts, versioning, authentication, authorization, error handling, logging, and service-to-service communication.
• Understand the principles and tradeoffs associated with monolithic versus microservice architectures.
• Build services that can be independently developed, tested, deployed, and scaled where appropriate.
• Understand asynchronous processing, messaging, and event-driven patterns.
• Apply pragmatic architectural decisions based on business and technical requirements rather than introducing unnecessary complexity.

Data & Entity Framework

• Strong working knowledge of Entity Framework Core (EF Core).
• Develop and maintain data access layers using EF Core.
• Understand Code First, database migrations, LINQ, relationships, transactions, and change tracking.
• Diagnose and optimize database queries and application performance.
• Experience working with SQL Server and relational database concepts.
• Understand when direct SQL, stored procedures, or alternative data-access approaches may be more appropriate than ORM-based solutions.

Team & Delivery

• Contribute as a team member to Agile projects and Scrum team workflows.
• Develop and unit test web application features across back-end and front-end, including maintenance and support.
• Support and collaborate with teams across design, development, quality assurance, and operations.