SENIOR BACKEND DEVELOPER (PAYMENT RECONCILIATION)

Working location: Gia Dinh Ward (Binh Thanh District), Ho Chi Minh City
Salary range: Up to VND 80,000,000 gross
INFORMATION
Payment Reconciliation is the process of matching every incoming and outgoing payment against what their systems expect - invoices, refunds, chargebacks, and the settlement files they receive from banks and payment providers. Manually, it doesn't scale. Automated, it runs quietly in the background, flags only the cases that need a human decision, and gives Finance an auditable view of every euro. That's what this team will build, from scratch.
As a Senior Backend Developer, you will:
●Build the services behind our reconciliation engine: ingesting and normalising provider files,
matching at scale, handling exceptions.
●Own correctness: idempotent processing, traceable matches, safe reprocessing of historical data.
●Integrate new banks and payment providers and keep those integrations maintainable.
●Translate accounting rules into testable software, together with Product and Finance.
●Shape the architecture of a greenfield system and set the engineering standard for it.
Team
The team will be newly established. You will work with a Senior Frontend Developer and an
Engineering Manager in the Ho Chi Minh City office, collaborating closely with engineering teams in
Germany and Vietnam and with the Product Managers in Germany. As one of the first engineers,
you'll influence both the technical foundations and how the team works across two locations.
RESPONSIBILITIES
●You design and build the services behind our payment reconciliation engine - ingesting settlement and payout files from banks and payment providers, normalising them, and matching them against our own transaction data.
●You implement the matching logic and the exception handling around it: what matches automatically, what lands in a review queue, and how a human resolves it.
●You own correctness in a domain where it is not negotiable - idempotent processing,
traceable matches, and safe reprocessing of historical data without corrupting what has already been reconciled.
●You integrate new banks and payment service providers, and keep those integrations maintainable as formats and requirements change.
●You translate accounting and finance rules into software that is readable and testable,
working directly with Product and our Finance stakeholders.
●You make the architectural decisions for a greenfield system - module boundaries, data model, and how reconciliation fits into our wider platform.
●You keep the system observable and operable: clear logs, meaningful metrics, and a clean answer to "why did this transaction not match?".
●You review code, share context with the front-end engineer on the team, and help set the engineering standard for a team that is just starting out
REQUIREMENTS
●Several years of professional experience in backend development with C# and .NET.
●Deep understanding of application architecture - modular monoliths, bounded contexts, and where to draw the line between them.
●Hands-on experience with CQRS and the REPR / vertical-slice style: one class per use case instead of growing service classes.
●Experience with the repository pattern and with NoSQL or document databases (e.g. Azure
Cosmos DB).
●Familiarity with modern API frameworks (e.g. FastEndpoints, Minimal APIs) and object mapping (e.g. Mapster, AutoMapper).
●A strong grasp of dependency injection and how to keep composition roots thin.
●Solid testing practice - unit and integration tests, and an eye for what makes code testable in the first place.
●Confident with Git and collaborative workflows: pull requests, code reviews, and giving feedback that lands A big plus:
●Experience with CI/CD pipelines (GitHub Actions) and basic knowledge of Kubernetes and Helm.