Senior .NET Engineer — Microservices, Kafka, AWS

High-load event-driven microservices on ASP.NET Core, Kafka and AWS — 7 years in cross-border e-commerce checkout, payments and iGaming. I own services end to end: design, API contracts, messaging, data, CI/CD and production. Warsaw, CET.

• .Net
• Amazon Web Services (AWS)2 J.
• Apache Kafka2 J.
• ASP.NET6 J.
• C#6 J.
• Docker
• Kubernetes2 J.
• Microservice
• Postgresql1 J.
• Terraform

Senior .NET Engineer building high-load, event-driven microservices on ASP.NET Core, Kafka and AWS — 7 years across cross-border e-commerce checkout, payments, iGaming and healthcare. I own services end to end: system design, API contracts, messaging, data, CI/CD and production.

WHAT I DO
- Distributed systems: event-driven architecture, DDD, CQRS, SAGA, idempotency and resilience patterns on Kafka, RabbitMQ and MassTransit
- Cloud-native .NET on AWS (EKS, SQS/SNS, S3, RDS) and Kubernetes — services running under real cross-border e-commerce traffic
- Platform leverage: service templates, internal SDKs, test automation — infrastructure that makes every other engineer on the team faster

SELECTED RESULTS
- Designed and built a Checkout API microservice from scratch (ASP.NET Core, Kafka, Couchbase) and led its zero-downtime cutover
- Built a Spreedly-based payment-processor integration layer that cut onboarding of a new provider (PayPal, CyberSource) from 1-2 months to 1 day
- Migrated 200,000 subscriptions / 800,000 subscription items — six years of production data — with no customer-visible downtime
- Cut new microservice bootstrap time by 80% with API and worker templates adopted by every Scrum team
- Delivered a sportsbook integration generating 30% of total GGR on a real-money iGaming platform
- Raised microservice test coverage from 20% to 85%, cutting 2-6 hours off every feature delivery

HOW I WORK
Async-first: written specs, decisions in writing, deep-work blocks. AI-native workflow — spec-driven development, Claude Code and Cursor, custom MCP servers against the codebase.

Based in Warsaw, CET — full overlap with the German working day. Polish sole proprietorship: I invoice EU clients directly under reverse charge (EU reverse charge, VAT-EU), no EOR needed.
English B2 (British Council), Ukrainian native.

WHAT I DO
- Distributed systems: event-driven architecture, DDD, CQRS, SAGA, idempotency and resilience patterns on Kafka, RabbitMQ and MassTransit
- Cloud-native .NET on AWS (EKS, SQS/SNS, S3, RDS) and Kubernetes — services running under real cross-border e-commerce traffic
- Platform leverage: service templates, internal SDKs, test automation — infrastructure that makes every other engineer on the team faster