Senior .NET Developer

Quick Facts

• Role: Senior .NET Developer

• Work mode: 100% remote

• Location: Warsaw or Kraków

Description

You will join a team modernizing an existing application—raising security, stability, and maintainability. The project covers security hardening, redesign of data import/export processes, integration modernization, and introduction of modern authentication mechanisms. A key task is replacing direct database link connections (DB Link) with secure API interfaces.

Responsibilities

• Identify and remediate vulnerabilities in application code following security standards

• Analyze current architecture and modernize components safely

• Redesign data import to ensure performance, stability, and high-quality error handling

• Design and implement secure REST APIs replacing DB Link communication

• Design and implement multi-factor authentication (MFA)

• Use OAuth 2.0 and OpenID Connect for authentication and authorization

• Optimize data export processes and adjust the file interface

• Develop and modify business logic for generating and delivering files

• Maintain code quality with a focus on testability and security

• Collaborate with architecture, security, and other project stakeholders

• Identify technical risks and recommend solutions supporting application continuity

Requirements

• Several years of experience developing applications with C# and .NET/.NET Core 5+

• Very strong design patterns knowledge, multithreading, and performance optimization

• Practical experience building secure, scalable REST APIs

• Knowledge of application security, including OWASP Top 10

• Experience implementing authentication/authorization: OAuth 2.0, OpenID Connect, and MFA

• Advanced SQL and relational database knowledge

• Experience designing and supporting import/export processes

• Knowledge of integrations in distributed systems and file interfaces

• Experience with safe refactoring and modernization of existing systems

• Experience creating unit and integration tests

• Knowledge of Clean Code and good software engineering practices

• Agile experience (Scrum or Kanban)

• Familiarity with tooling for software delivery and collaboration (Git, Jira, Azure DevOps)

• Independence, proactivity, and ability to communicate technical decisions

• Readiness to work with security and architecture teams

Benefits

• Collaboration with an interdisciplinary team of technology enthusiasts

• Long-term project involvement in an IT organization active for 20+ years

• Opportunity to work on diverse IT projects for recognizable clients

• Access to latest technologies and engineering standards

• Flexible service terms: hybrid or fully remote depending on the engagement

• Knowledge-sharing ecosystem: internal trainings, thematic guilds, cloud trainings and certifications via partnerships

• Access to online English/German learning and group classes

• Multisport and private medical care on preferential terms

• Company-sponsored sailing trips in the Caribbean, Mediterranean, and Northern seas