Middle Strong .NET Developer, short-term cooperation

We are looking for a Middle Strong .NET Developer to join a fintech project focused on building a real-time digital payments platform. You will design and develop scalable .NET microservices, integrate with payment providers and banking partners, and shape the backend architecture of a secure, high-load system. This role offers high ownership and direct impact on a rapidly evolving product.

This is initially a full-time, short-term collaboration that will last up to 2,5 months, with the possibility of extension.

About the project

Real-time digital payments platform enabling low-friction, secure QR-based payments for in-person and online transactions. The product integrates with a payment gateway, supports WhatsApp-based onboarding and payment journeys, and provides a Merchant Portal for real-time payment, QR generation, and payout configuration. The backend is planned as .NET microservices hosted on Azure with a SQL datastore, plus integrations with payment processors and banking partners.

Responsibilities

• Design, build, and maintain .NET microservices that power RTP, QR payment flows, merchant operations, and API integrations.
• Implement secure, reliable integrations with:
  • RTP initiation and processing
  • Payment processors (e.g., Peach, Stitch, PaySoft)
  • WhatsApp APIs for onboarding and payment journeys
  • Merchant platform capabilities (QR generation, payout configuration, real-time tracking).
• Build and maintain external-facing APIs for online merchants and potential white-label implementations.
• Implement observability (structured logging, metrics, tracing), incident readiness, and operational runbooks.
• Enforce code quality via clean architecture, testing strategy, code reviews, and CI/CD.
• Contribute to security/compliance implementation aligned with fintech expectations (PII protection, secrets management, auditability).
• Use AI-assisted development tools in day-to-day work to accelerate delivery while maintaining correctness, security, and maintainability.

Required experience and skills

• 3+ years of professional software engineering experience; strong senior-level ownership and delivery track record.
• Strong .NET experience (C#, ASP.NET Core) building production APIs and microservices.
• Microservices and distributed systems experience: async processing, idempotency, retries, eventual consistency, and fault tolerance.
• Strong API design skills (REST; event-driven patterns where appropriate) and integration-heavy systems experience.
• Strong SQL skills (schema design, transactions, performance tuning) with production RDBMS (e.g., PostgreSQL, SQL Server).
• Cloud experience on AWS or Azure, including containerized deployments and managed services.
• CI/CD, automated testing, and production operations experience.
• 1+ year of experience using AI-assisted development tools (e.g., CodexClaude Code, GitHub Copilot, Cursor) to accelerate system design, development, debugging, and testing while maintaining high code quality.
• Ability to critically evaluate and harden AI-generated solutions, ensuring correctness, security, and maintainability in production systems.

Nice to have

• Experience building systems that handle money movement, payments, or other regulated financial workflows.
• Practical knowledge of transaction integrity concepts: reconciliation, audit trails, idempotency keys, strong consistency where required, and secure handling of sensitive data.
• Security-first mindset: threat modeling, secure API auth, encryption practices, and least-privilege access.
• Experience with real-time payments / RTP-like flows, QR payments, or bank/payment-provider integrations.
• Experience with WhatsApp or similar conversational-channel integrations.
• Experience with event streaming/message brokers (Kafka, RabbitMQ, Azure Service Bus, SQS/SNS).
• Experience building merchant portals/admin platforms (even if not primary focus).
• Exposure to PCI-like controls and fintech compliance processes (as applicable to the product).

Communication

• Strong English communication for technical discussions, documentation, and partner collaboration.
• Comfortable working with a startup cadence: ambiguity, fast iteration, and high ownership.