# Backend Engineering > Selected Engineer ApS work demonstrating Backend Engineering — the achievements that prove it. - [Improved geographical map application performance by 10x through strategic database transition from MSSQL to PostgreSQL, optimizing processing and data security.](https://engineer.company/portfolio/improved-geographical-map-application-performance-by-10x-through-6/) - [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://engineer.company/portfolio/delivered-8-power-bi-projects-with-comprehensive-manuals-10/) - [Directed full‑stack GIS map development, overseeing PostgreSQL, Mapbox, ReactJS, and NodeJS to deliver an integrated solution.](https://engineer.company/portfolio/directed-full-stack-gis-map-development-overseeing-postgresql-25/) - [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://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://engineer.company/portfolio/developed-a-data-analytics-reporting-system-increasing-quarterly-44/) - [Developed 100 web applications using HTML/HTML5, CSS/SCSS, Django, WordPress, and Joomla frameworks, ensuring diverse online presence.](https://engineer.company/portfolio/developed-100-web-applications-using-html-html5-css-51/) - [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://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://engineer.company/portfolio/designed-a-json-passthrough-architecture-where-postgresql-functions-58/) - [Designed an organization context‑switching system with client localStorage and server‑side cookie mirroring, letting users act as managed organizations while enforcing least‑privilege authorization.](https://engineer.company/portfolio/designed-an-organization-context-switching-system-with-client-59/) - [Migrated the HTTP API from Fiber to Huma v2 — 649 paths and 760 operations — reaching and holding 100% parity between the routes the server registers and the OpenAPI description it publishes.](https://engineer.company/portfolio/migrated-the-http-api-from-fiber-to-huma-60/) - [Generated the API contract outward from the database — OpenAPI, a 44,076‑line typed TypeScript client, 61 mock handlers and the limits the UI enforces — with a guard at every hop that fails on drift.](https://engineer.company/portfolio/built-a-request-schema-validation-contract-with-automated-61/) - [Built email as a platform capability — three providers with failover, delivery webhooks, send and delivery logging, templating and campaigns — behind a startup check that will not boot without one.](https://engineer.company/portfolio/built-email-as-a-platform-capability-with-failover-62/) - [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://engineer.company/portfolio/designed-a-postgresql-function-first-data-layer-across-63/) - [Adopted UUID v7 time‑ordered identifiers (PostgreSQL 18) as entity keys to reduce B‑tree index fragmentation and speed up queries.](https://engineer.company/portfolio/adopted-uuid-v7-time-ordered-identifiers-postgresql-18-64/) - [Implemented a catalogue‑driven deep‑merge for stored JSON preferences, preventing missing‑key crashes as the schema evolves.](https://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://engineer.company/portfolio/built-a-python-vessel-data-scraper-marinetraffic-maritime-66/) - [Hardened the application with nonce‑based CSP, HSTS, SameSite cookies, least‑privilege database roles and server‑side entitlement re‑checks.](https://engineer.company/portfolio/hardened-the-application-with-nonce-based-csp-hsts-77/) - [Set the platform's founding decisions in the weeks after the repository opened in November 2025 — the layering, database‑first data access and the zero‑warnings bar — and they still hold nine months on.](https://engineer.company/portfolio/set-the-platform-s-founding-decisions-in-november-2025-80/) - [Developed and maintained Django web applications for the IPTV platform, shipping new features and improving performance and stability.](https://engineer.company/portfolio/developed-and-maintained-django-web-applications-for-the-84/) - [Built a layered automated test suite — 981 Go tests, 543 frontend and browser specs, 494 SQL behavioural tests — with mutation testing, property‑based tests and an accessibility gate.](https://engineer.company/portfolio/built-a-layered-automated-test-suite-across-four-layers-94/) - [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://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://engineer.company/portfolio/moved-slow-work-onto-a-river-job-queue-97/) - [Built first‑party error monitoring and OpenTelemetry tracing rather than buying them — payload sanitising, spike and regression detection, symbolication and a synthetic heartbeat — behind 11 operator views.](https://engineer.company/portfolio/built-first-party-error-monitoring-and-tracing-98/) - [Built fail‑closed abuse controls — 22 Redis‑backed rate limiters, Cloudflare Turnstile, request idempotency and an origin lock — so the platform sheds bots and floods instead of trusting its callers.](https://engineer.company/portfolio/built-fail-closed-abuse-controls-and-rate-limiting-100/) - [Built the operator back‑office — around 40 admin routes and 128 components covering claims, moderation, feature flags, cache and diagnostics — so the platform can be run without database access.](https://engineer.company/portfolio/built-the-operator-back-office-for-the-platform-102/) - [Built company ownership claims end to end — a user claims a company, an administrator adjudicates, and an approval rewrites the authorization graph that decides who is allowed to edit what.](https://engineer.company/portfolio/built-company-ownership-claims-end-to-end-103/) - [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://engineer.company/portfolio/built-the-loyalty-and-reputation-system-105/) - [Built the platform's social layer — posts, feed, groups, mentions, a follower graph and an occasions digest — on the same function‑first data layer as the rest of the product.](https://engineer.company/portfolio/built-the-platform-s-social-layer-106/) - [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://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://engineer.company/portfolio/built-a-database-driven-cv-and-portfolio-generator-144/) - [Vendored a QR encoder — Reed‑Solomon over GF(256), fixed module layout, eight mask patterns — in 522 lines rather than take a third runtime dependency, and verified it by reading the finished matrix back with an independently written decoder.](https://engineer.company/portfolio/vendored-a-qr-encoder-in-522-lines-148/) - [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://engineer.company/portfolio/moved-every-user-facing-string-into-a-content-tree-152/) - [Adopted Swift 6 complete strict concurrency with no actors, bridging a blocking C event loop to the main actor through one producer, one consumer and one ordering — after establishing that a task per event loses the ordering the interface depends on.](https://engineer.company/portfolio/adopted-swift-6-strict-concurrency-over-a-c-event-loop-156/) - [Wrote a parser that reads the real 7,308‑line C header and verifies every call site, every enum constant and that every pointer‑owning class is final, after a hand‑written placeholder header let calls to three removed functions compile, link and crash.](https://engineer.company/portfolio/wrote-a-parser-that-verifies-every-ffi-call-site-157/) - [Reached the half of the messaging core the application had never used — backup transfer, disappearing messages, message editing and resending, verified invitations, proxies and encryption policy — driving every test against the real library with no mocks.](https://engineer.company/portfolio/reached-the-unused-half-of-the-messaging-core-161/)