Stefan Amann

Design and implementation of a compact ERP, CRM, accounting, and production-planning platform for a German food manufacturer. The system replaces Rechnung11, self-built Excel sheets, and manual processes for fewer than 10 internal users.

• • Designed and implemented the full platform architecture as sole architect and developer.

• • Built modules for customer management, B2B order handling, invoicing, production planning, and accounting support.

• • Implemented DATEV export, ZUGFeRD/XRechnung e-invoicing, FinTS bank statement synchronization, and GoBD audit trail concepts.

• • Used AI-supported workflows for prototyping, test support, and implementation acceleration while retaining full architecture, review, testing strategy, and technical ownership. Technology: Java 23, Spring Boot 3, Spring Data JPA, Spring Security, Vue 3, TypeScript, PostgreSQL, Flyway, REST, OpenAPI, JWT, TOTP, RBAC, DATEV, FinTS, ZUGFeRD, XRechnung, GoBD, JUnit, Mockito, Testcontainers, Playwright, Docker, GitLab CI/CD

Backend engineering for a production secure-communication gateway connecting German health insurers to the national telematics infrastructure. The system supports regulated medical-data communication and message flows around FHIR, KIM, and TIM.

• • Shipped backend features and bug fixes for the gematik telematics gateway connecting German health insurers to TI.

• • Built Java/Spring services for FHIR, KIM, and TIM message handling and integration flows.

• • Hardened cryptographic message handling (PKI, hashing, digital signatures) across secure communication paths.

• • Resolved 5 major production bugs and raised test coverage around secure message processing and integration flows. Technology: Java, Java EE, Spring, Spring Boot, Spring Data, FHIR, KIM, TIM, REST, SMTP, POP3, LDAP, PKI, cryptography, MongoDB, Kubernetes, Docker, OpenAPI, GitLab, Nexus

Backend engineering and architecture for an energy-sector B2B SaaS platform built on Go and Java microservices running on Kubernetes and AWS. Owned end-to-end document workflows. Generation, persistence/archiving, printing, and delivery. Also replaced internal print and mailing workflows with Deutsche Post API integration. Work also covered feature delivery, performance profiling, prototyping, OAuth2/JWT-secured APIs, and CI/CD workflows.

• • Built Go and Java microservices for an energy-sector B2B SaaS platform on Kubernetes and AWS.

• • Owned end-to-end document workflows covering generation, persistence/archiving, printing, and delivery.

• • Replaced internal print and mailing workflows with a Deutsche Post API integration.

• • Built REST/OpenAPI service interfaces and OAuth2/JWT-secured authentication flows. Technology: Go, Java, Quarkus, Spring Boot, Spring Data, REST, OpenAPI, OAuth2, JWT, AWS Aurora, RDS, S3, Cognito, PostgreSQL, MySQL, Kubernetes, Docker, GitHub, Jenkins, Drone