Senior Backend Engineer — Data Platform & API

NAXCON GmbH, located in the heart of Freiburg, is at the forefront of the German IT and engineering industry.Our experts have extensive knowledge in software and hardware development, state-of-the-art electronics, and future-oriented technologies such as artificial intelligence and virtual reality.We are not only dedicated to project work for our customers, but also intensively pursue in-house innovation projects as well as research & development. Renowned companies from a wide range of German industries place their trust in us - demonstrating the outstanding expertise and commitment of our engineers.Position: Senior Backend Engineer — Data Platform & APIType: Full-time/RemoteField: Development of Information PlatformAbout the Role:The Senior Backend Engineer leads the data platform and API workstream and serves as formal deputy to the Project Lead. This person architects and builds a three-layer PostgreSQL/PostGIS/H3 database, two structurally different ETL pipelines ingesting 50,000+ spatial data points per inventory cycle, and the FastAPI REST layer that powers all frontend components including the geospatial dashboard and embeddable widget.The role requires deep expertise in spatial databases and Python backend development, combined with the communication skills to act as client-facing deputy. All API endpoints must be covered by automated integration tests that serve as CI deployment gates. A Software Bill of Materials (SBOM) in CycloneDX or SPDX format must be maintained and delivered at every milestone.Key Responsibilities:Design three-layer PostgreSQL schema Architect and implement the raw, canonical, and materialised-aggregate database layers. Define data types, spatial columns, H3 cell attribution, and aggregation routines across five administrative spatial levels (Bundesland, Landkreis, Hegegemeinschaft, Forstamt, Revier) and yearly time ranges.Build and operate ETL pipelines Develop two structurally different Apache Airflow ETL pipelines: one consuming GeoJSON FeatureCollections from the Brandenburg OGC API (with linked-graph traversal), and one ingesting CSV files from Mecklenburg-Vorpommern (with GIS-layer coordinate resolution). Implement error logging, reconciliation, and manual-trigger capability.Implement FastAPI REST layer Deliver the public REST API with OpenAPI 3.1 schema documentation, at minimum three endpoints (GET /schema, GET /data/values, GET /data/raw), pagination, location anonymisation, GeoJSON output, and an optional async export mechanism. All endpoints must have automated integration test coverage.Design and implement caching strategy Architect and implement Redis-based server-side caching for frequently aggregated API responses, with ETL-aligned cache invalidation, appropriate HTTP caching headers, and documented cache-duration rules — ensuring p95 latency under 3 seconds for default dashboard filter sets.Security and access control Implement OAuth2/OIDC authentication via Keycloak, IP- and token-based rate limiting, throttling, and TLS/WAF configuration. Ensure all API design choices are DSGVO-compliant (data minimisation, anonymisation of coordinates in raw endpoint).Performance and spatial indexing Define and maintain GIST/BRIN spatial indexes, materialised views for pre-aggregated query paths, and query optimisation strategies. Ensure standard-filter dashboard map load under 3 seconds and custom-filter map load under 5 seconds at p95.Deputy project lead Act as deputy to the Project Lead — attend all client milestone reviews, maintain scope decisions and technical risk log, and serve as sole client-facing representative when the Project Lead is unavailable.SBOM and documentation Produce and maintain a Software Bill of Materials (SBOM) in CycloneDX or SPDX format at every delivery milestone. Document the API, ETL logic, and database schema in a form sufficient for independent operation and future development without the original contractor.Requirements:5+ years of professional backend development experience with Python, including production REST API delivery.3+ years of hands-on experience with PostgreSQL and PostGIS for spatial data applications — including schema design, spatial indexing, and query optimisation.Proven experience designing and implementing REST APIs using FastAPI or a comparable async Python framework, with OpenAPI schema generation.Experience building and operating ETL pipelines with a workflow orchestration tool (Apache Airflow or equivalent).Working knowledge of Redis for API caching, including cache invalidation strategies tied to data update events.Familiarity with OAuth2/OIDC authentication flows and API security practices (rate limiting, throttling, WAF).Fluent German at minimum C1 level — mandatory per Anlage B §7.1.Nice to Have:Experience with H3 hexagonal spatial indexing in a PostgreSQL/PostGIS or pipeline context.Knowledge of OGC API Features, WFS, and GeoJSON FeatureCollection structures.Experience with Keycloak or another open-source identity provider for OAuth2/OIDC.Familiarity with DSGVO-compliant API design patterns (coordinate anonymisation, pseudonymisation, log retention policies).Prior delivery on a German public-sector, open-source, or institutional data platform project.Experience with GeoAlchemy2 or similar Python spatial ORM libraries.Familiarity with SBOM standards (CycloneDX or SPDX) and software supply chain transparency.Experience with Hetzner Cloud or comparable European hosting infrastructure.What we offer:Join a cosmopolitan and internationally mixed team: We welcome individuals from all backgrounds and cultures to contribute their unique perspectives and talents to our team.Polish your German language skills: If you are looking to improve your German language skills, we offer a supportive environment where you can practice and develop your language abilities: whether you are a beginner or an advanced speaker.Benefit from a fixed contact person from the company: We understand the importance of having a reliable point of contact within the company. That's why we assign a dedicated contact person who will provide guidance and support throughout your employment with us.Professional growth and development: With us, our engineers can immerse themselves in new industries or projects after just 1-2 years and actively transfer knowledge.Enjoy regular team events with the company: We believe in the power of team building and fostering positive relationships within the workplace. That's why we organize regular team events to promote collaboration and strengthen our team bonds.Competitive compensation package: At NAXCON, we believe that our engineers are our greatest asset. That's why we offer a comprehensive and competitive compensation package that includes a salary commensurate with experience and expertise.