Retail & automotive trade
06
Accounting OS
GoBD-compliant accounting & warehouse system
HD Autoservice01/2024 – 12/2024 · ~12 months · ongoing maintenance (side project) · Sole developer · full-stack & AI
Role
Sole developer · full-stack & AI
Team
Solo · client project
Location
Salzgitter, DE · remote
Language
German
Visibility
Internal system
Methodology
Self-directed
Responsibilities
- Accounting module: invoices, corrective invoices, PDF export, customer management, order import with GoBD-compliant record locking.
- Coupling of warehouse management and invoicing (automatic stock deduction, minimum-stock notifications).
- A resilient data synchronisation service (“pipe service”) for supplier catalogues — up to 20 m CSV rows over TLS with a queue, caching, retry logic, validation and deduplication.
- Recursive resolution of foreign-key dependencies in the input dialogs, for consistent master data maintenance.
- Customer and master data management with role-based access control (admin, staff, tax adviser) and authentication via better-auth; type-safe GraphQL and REST interfaces (NestJS, MikroORM, DTOs).
- Technical advice for the client on approaches, architecture and process optimisation.
- Self-hosted delivery on Linux servers (Docker) with a CI/CD pipeline (GitHub Actions) and automated quality checks before every commit (Husky).
- Sole responsibility for the architecture (clean architecture), deployment and ongoing support (side project): maintenance, security updates and further development.
Outcome
- According to the client, up to 40 hours less administrative work per month — roughly 480 hours a year.
- According to the client, routine processes take up to 50 % less time.
- End-to-end digital, GoBD-compliant workflows with warehouse and accounting directly coupled.
- In continuous operation since go-live: delivery, security updates and further development keep running automatically, without the client having to maintain an IT function for it.
- Daily automatic synchronisation of every supplier's car parts catalogue with Accounting OS — stock and prices are in place without a manual import.
Testimonial
Technologies
TypeScriptJavaScriptSQLHTMLCSSJSONYAMLNode.jsNestJSFastifyDependency InjectionNext.jsReactServer-Side Rendering (SSR)TanStack QueryTailwind CSSStorybookREST APIGraphQLDTOsType safetyBackend developmentFrontend developmentWeb developmentData synchronisationCSV processingETLMessage QueuesCachingIdempotencyResilience PatternsMariaDBPostgreSQLRedisMikroORMTypeORMData modellingInventory managementWarehouse managementAccountingInvoicingOrder managementMaster data managementPDF generationERPGoBDAudit-proof recordsProcess digitalisationDigital transformationbetter-authJWTRole-Based Access Control (RBAC)SSL/TLSIT securityDockerDocker ComposeDigital OceanSelf-HostingLinuxUbuntuMonitoringObservabilityCI/CDContinuous IntegrationGitHubGitHub ActionsHuskynpmCLI (Command Line Interface)MiroUnit TestingTest automationClaude CodeCursor AIModel Context Protocol (MCP)Agentic CodingAgentic pull request workflowsMonorepoNxMicroservicesDomain-Driven DesignScalable architectureClean CodeSOLIDClean ArchitectureRequirements EngineeringIT consultingSoftware developmentProduct ownershipEntrepreneurshipInterface developmentAPI integrationRequirements analysis