[WAP] Senior Full-Stack Developer (React, .NET)

Software Mind; Warszawa; Remote; PLN 223,000 - 446,000; Full time

Benefits offered by this job

Flexible remote cooperation

International projects with global NLP

Private healthcare and life insurance

Language classes

Knowledge-sharing initiatives

Multisport card

Job summary

Software Mind is seeking a senior software engineer in Warsaw to own C#/.NET services and REST APIs, collaborating with a small AI-first delivery team. You will design, implement, and test APIs, ensure security and PCI-safe data handling, and contribute to frontend work using React and TypeScript.

The role embraces flexible and remote cooperation options with international projects and a non-corporate atmosphere, offering private healthcare and language learning benefits.

Qualifications

• 7+ years of commercial software development experience.
• 5+ years of production-grade C#/.NET (ASP.NET Core, async, DI, EF Core or Dapper).
• Strong API design with REST, OpenAPI, versioning.
• Proficient in React and TypeScript for end-to-end features.
• Hands-on use of agentic AI coding tools and production-grade testing.

Responsibilities

• Design, build and ship production C#/.NET services and REST APIs under PCI DSS constraints.
• Own API contracts with the front end and versioning.
• Write efficient data access against relational databases at analyst-scale volumes.
• Implement authentication, authorization, audit logging and PCI-safe handling.
• Contribute to React/TypeScript front end and review frontend code.
• Use AI coding tools to accelerate development with solid test coverage.
• Maintain Dockerfiles, Compose configs and support AKS deployments.

Skills

C#/.NET

ASP.NET Core

API design

OpenAPI contracts

React & TypeScript

Docker & Kubernetes

CI/CD

SQL / Relational DB

Testing (xUnit/NUnit)

AI coding tools

Tools

Docker

Docker Compose

Kubernetes

Azure DevOps

GitHub Actions

EF Core / Dapper

Testcontainers

SQL Server

Job description

• Full-time

Company Description

Software Mind develops solutions that make an impact for companies around the globe. Tech giants & unicorns, transformative projects, emerging technologies and limitless opportunities – these are a few words that describe an average day for us. Building cross-functional engineering teams that take ownership and crave more means we’re always on the lookout for talented people who bring passion and creativity to every project. Our culture embraces openness, acts with respect, shows grit & guts and combines cooperation with enjoyment.

Job Description

Project – the aim you’ll have

Join a next-generation risk analysis and scoring platform built for a payments technology company. The platform combines the client’s own risk rules with AI-driven, pre-scored risk feeds from a global card network over high-volume payment data under PCI DSS. You’ll own the C#/.NET services and API contracts the analyst-facing apps run on, in a small AI-first delivery team alongside a frontend-leaning developer.

Role – how you’ll contribute

• Design, build and ship production C#/.NET services and REST APIs serving high-volume payment and risk data under PCI DSS constraints
• Own API contracts with the front end: typed OpenAPI contracts, versioning and backward-compatible change
• Write efficient data access against the operational database and Microsoft Fabric Gold-layer risk tables at analyst-scale volumes
• Implement security-critical concerns: authentication, authorization, audit logging and PCI-safe handling of tokenized card data
• Contribute to the React and TypeScript front end – building features end to end, reviewing and pairing
• Use Claude Code or an equivalent agentic coding tool as your primary accelerator, backed by unit, integration and contract tests, while owning the quality of every line merged
• Maintain Dockerfiles and Compose configurations, support deployments to AKS and contribute to Azure DevOps CI/CD
• Implement against the target architecture set by the client’s architecture group, raise risks early and hand off work the internal team can own

Qualifications

Expectations – the experience you need

• 7+ years of commercial software development, including 5+ years of production-grade C#/.NET (ASP.NET Core, async, DI, EF Core or Dapper)
• Strong API design: REST conventions, OpenAPI contracts, versioning and evolving APIs without breaking consumers
• Relational database and distributed-systems skills: schema design, query tuning, transactional correctness, idempotency, failure handling
• Working proficiency in React and TypeScript – able to build features end to end and review frontend code
• Daily, hands-on use of agentic AI coding tools (Claude Code, Cursor, Copilot Workspace, Codex or similar) and a track record of shipping AI-accelerated code that holds up in production – you’ll demo your workflow live
• Containers: Docker (multi-stage builds, hardening), Docker Compose and Kubernetes (AKS preferred)
• Testing discipline: xUnit or NUnit, integration testing with real dependencies (e.g. Testcontainers) and contract testing
• Git, CI/CD (Azure DevOps, GitHub Actions or similar) and autonomy in an existing codebase

Additional skills – the edge you have

• Payments, card processing, risk/fraud or merchant services experience, ideally with PCI-scoped systems
• Microsoft Fabric, Delta Lake or building APIs over analytical data stores
• Messaging and observability: Azure Service Bus, Event Hubs or Kafka; OpenTelemetry and Application Insights
• Identity standards: OAuth2/OIDC, Microsoft Entra ID, managed identity
• Python and exposure to LLM-integrated or agentic applications (e.g. LangGraph); prior consulting experience

Additional Information

What we offer:

• Flexible and remote cooperation options
• International projects with leading global clients
• Travels related to international projects
• Non-corporate atmosphere
• Access* to language classes
• Access* to knowledge-sharing initiatives
• Access* to private healthcare and life insurance
• Access* to multisport card

*The availability and terms of individual benefits may vary depending on the chosen form of cooperation.