.NET Backend Engineer

0TO9 is a bank for entrepreneurship built by and for financial innovators. We provide infrastructure for entrepreneurs ready to start and scale the next generation of financial products and platforms. Founded in Stockholm in 2025 were already 200 co-workers across Europe with offices in Stockholm and Berlin.

Our name reflects our mission: from zero to success from idea to impact from now to whats next.

At 0TO9 youll build the systems behind the next wave of fintech ventures. Its a chance to solve complex problems at scale on systems that are still young enough to shape.

• Build and maintain C#/.NET microservices on AWS ECS.

• Collaborate with product managers architects and engineers to deliver high-performance APIs

• Write clean testable code following SOLID principles.

• Apply DDD and CQRS to create modular scalable and maintainable systems.

• Design event-driven communication using NATS.

• Ensure reliability through idempotency retries and self-healing services.

• Implement observability: logging metrics tracing and performance monitoring.

• Work with both relational (MS SQL Server) and NoSQL (DynamoDB) databases.

• Contribute to secure design (auth secrets compliance).

• Improve CI/CD containerized workflows and engineering practices.

• Optionally follow a feature into the frontend (TypeScript React or Vue) when it needs to land end to end.

Agentic coding is our default not an experiment. Across the group we run a Claude-Code-native workspace:

• Engineering standards loaded as a skill so agents apply them automatically.

• A git-backed knowledge base that agents read and extend.

• Agent workflows that take a change from branch to reviewed PR.

• An automated reviewer in CI that counts as an approving review on a pull request.

Were looking for someone who already works this way and is comfortable making agents a normal part of how they build.

We think youll be a great fit if you:

• Have backend experience working with microservices and distributed systems C# and AWS.

• Take ownership challenge unclear requirements and prioritize reliability.

• Have applied DDD and CQRS in real-world systems.

• Understand event-driven architectures (ideally with NATS).

• Care about writing clean maintainable testable code.

• Already lean on LLMs and agentic tools daily you see them as leverage not a shortcut.

We build and SQL on the backend with TypeScript React and Vue on the frontend. This role lives on the backend and C# is a requirement. Frontend is a bonus not a bar.

Cloud & Infrastructure

• AWS-native: ECS/Fargate S3 least-privilege IAM.

• Container fluency: build ship and debug in production.

• Security by default: WAF encryption at rest and in transit.

• EU data residency: aware of why region matters.

Architecture

• Microservices & DDD: boundaries by domain not layer.

• API/event-driven: no shared databases.

• Resilience patterns: retries backoff idempotency.

• Clean SOLID code: safe for a human or an agent to extend.

Delivery & Quality

• CI/CD fluency: GitHub Actions or equivalent.

• Test-driven habits: 80% coverage no exceptions.

• Reviewable PRs: small diffs no self-merges.

• Supply-chain hygiene: dependency & SCA scanning before ship.

Observability & Security

• Structured logging & tracing: CloudWatch Datadog or equivalent.

• Zero hardcoded secrets: Secrets Manager or equivalent always.

• Encryption everywhere: KMS at rest TLS in transit.

Nice to have

• Previous fintech or banking industry experience youll ramp faster.

• Hands-on experience with integration testing contract testing or end-to-end service testing.

• Knowledge of observability tools and testing strategies for microservices.

• Understanding of cloud security governance and compliance.

• Frontend comfort in TypeScript React or Vue. Not required but its how you end up owning a feature end to end rather than half of one.

Find out more at wed love to hear from you.