# Backend & API Development > Selected work demonstrating this service. - [Designed, implemented, and administered 6 ETL/ELT pipelines, utilizing Google BigQuery, MSSQL, PostgreSQL, Shell scripting, PL/pgSQL, and Transact‑SQL, integrating data for efficient Python API processing.](https://data.engineer.company/portfolio/designed-implemented-and-administered-6-etl-elt-pipelines-8/) - [Delivered 8 Power BI projects with comprehensive manuals, integrating Microsoft Power BI tools with NodeJS API and Python FastAPI for effective data analytics and visualization.](https://data.engineer.company/portfolio/delivered-8-power-bi-projects-with-comprehensive-manuals-10/) - [Led the development, deployment, and support of over 30 GIS projects, demonstrating expertise in PostgreSQL, Bash, Python, JavaScript, GDAL, ArcGIS, PostGIS, and Mapbox technologies.](https://data.engineer.company/portfolio/led-the-development-deployment-and-support-of-over-35/) - [Developed a Data Analytics reporting system, increasing quarterly software revenue by 400% through Python‑based PDF reports.](https://data.engineer.company/portfolio/developed-a-data-analytics-reporting-system-increasing-quarterly-44/) - [Architected a layered maritime platform separating a Next.js PWA frontend, a Go (Huma/Fiber) API, and a PostgreSQL function layer, keeping all business logic in the database.](https://data.engineer.company/portfolio/architected-a-layered-maritime-platform-separating-a-next-57/) - [Designed a JSON passthrough architecture where PostgreSQL functions return complete JSON forwarded verbatim by the Go API, eliminating intermediate unmarshalling and decoupling the frontend from schema changes.](https://data.engineer.company/portfolio/designed-a-json-passthrough-architecture-where-postgresql-functions-58/) - [Designed a PostgreSQL function‑first data layer — 1,275 stored functions across 34 schemas — so every read and write goes through a function the database can grant, rather than through a table.](https://data.engineer.company/portfolio/designed-a-postgresql-function-first-data-layer-across-63/) - [Implemented a catalogue‑driven deep‑merge for stored JSON preferences, preventing missing‑key crashes as the schema evolves.](https://data.engineer.company/portfolio/implemented-a-catalogue-driven-deep-merge-for-stored-65/) - [Built the Python vessel‑data scrapers (MarineTraffic, Maritime‑Database) and a repeatable import that seeds the platform's reference data — 184,197 rows, including 698 companies and 56,149 vessels.](https://data.engineer.company/portfolio/built-a-python-vessel-data-scraper-marinetraffic-maritime-66/) - [Built the payments and entitlements layer — Stripe alongside Apple and Google in‑app purchase — gating the directory, search and export through an 11‑table access model checked on the server.](https://data.engineer.company/portfolio/built-the-payments-and-entitlements-layer-96/) - [Moved slow work off the request path onto a River job queue — 15 worker modules, 8 scheduled tasks and 20 pg_cron jobs — so a request returns while the work behind it carries on.](https://data.engineer.company/portfolio/moved-slow-work-onto-a-river-job-queue-97/) - [Built the loyalty and reputation system — 67 functions over a 31‑table ledger, with leagues, badges and a redemption shop — taking a row lock on the balance to close the double‑spend window.](https://data.engineer.company/portfolio/built-the-loyalty-and-reputation-system-105/) - [Built the hiring marketplace and the seafarer career workspace — 151 stored functions across 48 tables — covering vacancies, applications, certificates, rank progression and verified sea time.](https://data.engineer.company/portfolio/built-the-hiring-marketplace-and-career-workspace-107/) - [Built a database‑driven CV, references, portfolio and cover‑letter generator in Python — 41 modules, 10,580 lines — rendering six output formats from one 23‑table SQLite source assembled by a 19‑step idempotent pipeline.](https://data.engineer.company/portfolio/built-a-database-driven-cv-and-portfolio-generator-144/) - [Moved every user‑facing string out of Python into a content tree of 874 files across three languages, after finding dead translations nobody could see were dead and a check silently grading a third of the achievements.](https://data.engineer.company/portfolio/moved-every-user-facing-string-into-a-content-tree-152/)