Available for freelance, consulting & co-founder roles Based in Spain · Working worldwide · 2026

Guillem Climent

I build the infrastructure that runs a real, growing e-commerce business — because it runs mine.

Founder & sole technical architect of REUSALIA. I designed and built 100% of the platform's infrastructure and automation — the systems that move real inventory and real money. These patterns transfer to any operations-heavy business.

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ERP
in production, built by me alone
5
people I lead & trained
100%
of my company's workflow, automated
01

System Architecture

The REUSALIA platform — an end-to-end pipeline that moves data from public marketplaces, through processing and a custom ERP core, out to live storefronts and physical hardware on the warehouse floor.

Everything routes through a single source of truth. Data sources feed a processing layer, which writes to the ERP core, which in turn drives outputs — from marketplace listings to label printers running on local hardware.

Inputs01

Data Sources

  • 12 Wallapop accounts (private API)
  • eBay marketplace integration
  • Amazon product catalog scraping
  • Supplier & Google Sheets feeds
Pipeline02

Processing

  • Extraction & normalization
  • GPT-powered AI enrichment
  • Business-rules & validation layer
  • Celery async task queue
Core03

Custom ERP

  • PostgreSQL single source of truth
  • 25+ database models, FastAPI services
  • Retool / Angular operations frontend
  • 40,000+ live references
Outputs04

Outputs

  • Multi-platform listing sync
  • Order lifecycle automation
  • Cloud→local command bridge
  • Warehouse label printing

↳ Cloud-hosted core, with a database command-queue pattern bridging to local warehouse hardware in real time.

02

Selected Work

Production systems — not demos. Each ships against real inventory, real orders and real money. Source available on GitHub.

Flagship · 2023 — Present

The Full REUSALIA Platform

A complete, custom-built operating system for a circular e-commerce business: a marketplace extraction engine, AI enrichment pipeline, custom ERP, and cloud-to-local hardware workflows — designed, built and maintained as technical founder.

40,000+References
12 + eBayMarketplaces
~100/dayOrders processed
+50%Revenue YoY
PythonFastAPIPostgreSQL CeleryLLM / OpenAIRetoolHardware
01Reverse-engineered API

Wallapop Data Extractors

Reverse-engineered a marketplace's private API to sync orders at ~100/day, with resilient rate-limited extraction.

PythonReverse-engineeringResilient scraping
GitHub
02AI · ~40h/wk saved

AI Product Enrichment

Multi-stage LLM pipeline enriching thousands of items/day and saving ~40h every week.

PythonLLMOpenAI
GitHub
03Beats paid scrapers

Amazon Product Scraper

Production catalog scraper that outperforms paid scraping services — resilient and rate-limited at scale.

PythonSeleniumBeautifulSoup
GitHub
03

Experience Timeline

From enterprise consulting at scale to founding and engineering an entire platform. A through-line of building systems that have to work.

  1. Apr 2023 — PresentCurrent

    Founder & Technical Lead @ REUSALIA

    Sole architect of the entire platform. Built all backend, automation and the Retool ERP single-handedly. Lead, train and delegate to a 5-person team.

    FounderPython · FastAPIPostgreSQLTeam of 5
  2. Software Engineering

    Senior Software Engineer @ LittleBig Connection

    Senior engineering on production software at a platform connecting enterprises with technology talent — building and shipping robust backend services.

    BackendREST APIsCI/CD
  3. Consulting

    Software Engineer @ Sopra Steria · client: AIRBUS

    Engineering on mission-critical systems for AIRBUS — enterprise-grade software where reliability and rigor are non-negotiable.

    Java · Spring BootEnterpriseAerospace
  4. Consulting

    Software Engineer @ Capgemini · client: Mercadona

    Built and maintained software for Mercadona, one of Spain's largest retailers — high-volume retail systems operating at national scale.

    JavaOracle SQLRetail at scale
04

About & Resilience

In October 2024 a catastrophic flood hit. We rebuilt the company — and the systems that run it — from the ground up.

I founded REUSALIA at 25. Three years on it's a profitable, growing operation with a 5-person team, running entirely on infrastructure I designed and built alone — self-taught, iterating in production. I lead the team, teach each person their role, then delegate, review, correct, and iterate again.

At REUSALIA I architected and built the entire platform: a custom ERP backed by PostgreSQL, marketplace extraction engines that process roughly 100 orders a day, an AI enrichment pipeline that saves around 40 hours every week, and a cloud-to-local bridge that drives physical label printers on the warehouse floor.

Then, in October 2024, a catastrophic flood wiped out operations. Rather than walk away, we rebuilt — the warehouse, the team, and the software stack. That recovery is the part of my story I'm proudest of: it proved the systems were sound and the team was resilient. I don't just design architecture diagrams; I'm the founder who ships the code that brings them back online.

Guillem Climent Technical Founder · Systems Architect · Spain
05

Technical Writing

Long-form notes from the field — how the real systems were actually built, migrated and recovered.

  1. 01 How I Built a Full ERP Engineering 18 min read
  2. 02 How I Migrated a Production Business from Google Sheets to PostgreSQL Data 12 min read
  3. 03 From Manual Posting to Reverse Engineering Reverse engineering 14 min read
  4. 04 Rebuilding a Company After a Catastrophic Flood Resilience 10 min read
  5. 05 Bridging Cloud and Local: A Database Command Queue Pattern Architecture 6 min read
06

Skills & Stack

The tools behind the systems — from backend services and databases to specialized reverse-engineering and hardware integration.

01

AI & Agents

Production LLM pipelines (GPT-4o / 4o-mini)AI enrichment & classification at scaleGPT-vision document extractionAgentic tool-use & RAGEmbeddings / vector searchPrompt engineering
02

Backend

PythonFastAPIJavaSpring BootSQLModelREST APIsCelery
03

Databases

PostgreSQLMySQLOracle SQLNeonDBSQLite
04

Frontend

AngularVue.jsHTML / CSS / JSNgRxRetool
05

Specialized

API reverse-engineeringWeb scrapingBeautifulSoupSeleniumRate-limited / resilient scrapingLLM integrationData migration
06

DevOps

DockerJenkinsOpenShiftGitHub ActionsCI/CD
07

Work with me

Productized engagements — fixed scope, fast delivery, priced on outcomes. I take on a few clients at a time.

Project

Marketplace Automation

Multichannel listing, order and stock sync — built the way I run my own 40,000-reference operation.

Project

AI Data Enrichment

An LLM pipeline that turns raw product data into marketplace-ready listings at scale — eliminating ~40h/week of manual work.

Build + retainer

Scraping & Monitoring

Resilient, custom data extraction (prices, competitors, catalogs) that outperforms paid tools.

Monthly retainer

Fractional Engineer / CTO

Your part-time senior team: backend, automation, AI and data pipelines — production-grade, 1–2 days/week.

Tell me the problem — I'll tell you if I can save you time or money.

Book a 15-min call
08 — Contact

Let's build something that ships.

If you need production infrastructure that holds up under real load — or a technical co-founder who writes the code — I'd like to hear about it.

Open to · Freelance Consulting Technical co-founder opportunities
Email guillemclim@gmail.com GitHub github.com/AspiranteD LinkedIn linkedin.com/in/gcliment