Senior .NET Backend Engineer - Fintech Microservices on AWS

0TO9 | Bank of Entrepreneurship; Wrocław; On-site; PLN 180,000 - 280,000; Full time

Job summary

0TO9 is a bank for entrepreneurship, building fintech infrastructure across Europe. This backend-focused role will power microservices in C#/.NET on AWS, delivering high-performance APIs and reliable data platforms.

You'll collaborate with product managers and engineers, apply DDD/CQRS, implement observability, CI/CD, and security by default. Frontend work is optional but welcome for end-to-end features.

Qualifications

• Backend experience with C#/.NET, microservices, and AWS.
• Take ownership, challenge requirements, and prioritize reliability.
• Applied DDD and CQRS in real-world systems.
• Understand event-driven architectures (NATS preferred).
• Write clean, maintainable, and testable code.
• Leverage LLMs and agentic tools as a daily capability.

Responsibilities

• Build and maintain C#/.NET microservices on AWS ECS.
• Collaborate with product managers, architects, and engineers to deliver high-performance APIs.
• Apply SOLID principles and write clean code.
• Design modular, scalable systems using DDD and CQRS.
• Develop event-driven communication using NATS.
• Ensure reliability with idempotency, retries, and self-healing services.
• Improve observability with logging, metrics, tracing, and performance monitoring.
• Work with MS SQL Server and DynamoDB databases.
• Contribute to secure design (auth, secrets, compliance).
• Enhance CI/CD, containerized workflows, and engineering practices.
• Optionally contribute to frontend with TypeScript/React or Vue when needed.

Skills

C#

.NET

AWS

Microservices

DDD

CQRS

Event-driven

CI/CD

Tools

MS SQL Server

DynamoDB

NATS

GitHub Actions

Docker

ECS/Fargate

KMS

Secrets Manager

Job description

0TO9 is a bank for entrepreneurship, building fintech infrastructure across Europe. This backend-focused role will power microservices in C#/.NET on AWS, delivering high-performance APIs and reliable data platforms.

You'll collaborate with product managers and engineers, apply DDD/CQRS, implement observability, CI/CD, and security by default. Frontend work is optional but welcome for end-to-end features.