Senior .NET Engineer (Payment Platform)

Department: Backend Development

Location: Europe, Ukraine

Employment Type: FullTime

Fintech & AI-assisted | Remote | Full-time

About the company

Our client is building a high-load payment platform that processes thousands of transactions around the clock.

Their engineering challenges are far beyond typical CRUD applications. They build distributed systems where reliability, scalability, performance, and fault tolerance are critical. The platform is designed around an event-driven architecture using .NET 9, Kafka, PostgreSQL, Redis, and Docker.

If you're excited by solving complex backend problems and building systems that must never fail, we'd love to talk.

What you'll do

• Build and evolve the core of our payment platform.

• Design new services and payment provider integrations from architecture to production.

• Improve transaction processing, routing, and webhook infrastructure.

• Participate in architectural decisions and technical discussions.

• Review code, share knowledge, and help maintain a high engineering standard.

• Work closely with our Connector team (Python / TypeScript).

We're looking for someone who has

• Strong .NET expertise

• Deep knowledge of C# and .NET 8/9.

• Solid experience with ASP.NET Core.

• Strong understanding of asynchronous programming.

• Experience building highly concurrent applications.

• Production experience with Minimal API, Hosted Services and Dependency Injection.

• Experience building distributed systems

You understand concepts like:

• event-driven architecture;

• idempotency;

• Inbox / Outbox pattern;

• reliable message delivery;

• microservices;

• distributed transactions.

• Apache Kafka

Hands-on production experience with:

• consumer groups;

• at-least-once delivery;

• manual offset commits;

• idempotent consumers.

• Databases & Caching

• PostgreSQL;

• Dapper;

• SQL performance optimization;

• Redis / Valkey;

• caching strategies;

• Sentinel or Redis Cluster.

• Infrastructure

• Docker;

• container orchestration (Docker Swarm or Kubernetes);

• production deployments.

• FinTech experience

Ideally you've worked with:

• payment platforms;

• PayIn / PayOut flows;

• webhooks;

• callbacks;

• payment routing;

• cascade retry;

• HMAC signatures;

• replay attack protection;

• PCI DSS requirements.

• Engineering mindset.

You care about software quality and production reliability.

You regularly work with:

• unit and integration testing;

• structured logging;

• metrics;

• distributed tracing;

• observability.

• AI-assisted development

• AI is part of our engineering workflow.

We expect engineers to confidently use tools like Cursor, Claude Code, GitHub Copilot or similar while maintaining full ownership of the produced code.

Nice to have

• Lua / LuaJIT

• OpenAPI-first development

• openapi-generator

• Python or TypeScript

• Git Submodules

• Dynamic configuration through event buses

Tech Stack:

.NET 9 • ASP.NET Core • Kafka • PostgreSQL • Redis • Dapper • Docker • Event-driven Architecture • Microservices • OpenAPI • AI-assisted Development

Why join us?

• You'll work on a product where engineering decisions truly matter.

• Instead of maintaining legacy enterprise software, you'll help build the core infrastructure of a modern payment platform used in production every day.

• You'll join a team that values clean architecture, ownership, technical excellence, and continuous improvement.

• If solving challenging distributed systems problems motivates you, you'll feel at home here.