Senior .NET Fullstack Engineer – FinTech Backend Lead

Bonapolia; Polska; Remote; PLN 393,000 - 568,000; Full time

Job summary

Bonapolia seeks a senior backend-focused developer to design, build, and scale a multi-asset trade and portfolio management platform. You will work on backend services, APIs, and data pipelines, collaborating with frontend engineers to deliver client-facing SaaS solutions.

The role requires strong C#, .NET, ASP.NET Core, and SQL skills, plus experience with Angular and RESTful APIs. You’ll contribute to cloud architectures and distributed systems in an Agile, data-intensive environment.

Qualifications

• Bachelor’s degree in Computer Science, Engineering, or a related field.
• 5+ years of experience as a Full Stack Developer or Back-End Developer in FinTech or technology.
• Proficiency in C#, .NET, ASP.NET Core, Entity Framework, and SQL.
• Experience with Angular, JavaScript, and TypeScript.
• Experience designing and consuming RESTful APIs.
• Experience with relational and/or NoSQL databases.
• Familiarity with cloud-based architectures, distributed systems, and modern deployment practices.
• Experience working in Agile development environments.
• Ability to work independently while contributing effectively to a collaborative team.
• Experience supporting data-intensive, client-facing applications.

Responsibilities

• Design, build, and maintain backend services, APIs, and core application logic supporting client-facing platforms.
• Improve scalability, reliability, security, and performance.
• Collaborate with frontend engineers, product managers, and client-facing teams to translate business requirements into technical solutions.
• Develop and maintain data pipelines and integrations with internal and external systems.
• Write, maintain, and review automated unit and integration tests to ensure code quality and system stability.
• Troubleshoot production issues, optimize performance, and proactively identify technical risks.
• Contribute to software design discussions, code reviews, and documentation across the engineering team.
• Support end-to-end feature delivery from design through deployment and post-release monitoring.

Skills

C#

SQL

Angular

JavaScript

TypeScript

REST APIs

NoSQL

Cloud

Agile

Data pipelines

Unit testing

Education

Bachelor’s degree in Computer Science

Tools

.NET

ASP.NET Core

Entity Framework

Job description

Bonapolia seeks a senior backend-focused developer to design, build, and scale a multi-asset trade and portfolio management platform. You will work on backend services, APIs, and data pipelines, collaborating with frontend engineers to deliver client-facing SaaS solutions.

The role requires strong C#, .NET, ASP.NET Core, and SQL skills, plus experience with Angular and RESTful APIs. You’ll contribute to cloud architectures and distributed systems in an Agile, data-intensive environment.