# Stijn de Ruijter

> Freelance Data & Analytics Consultant based in the Netherlands. Helps scale-ups and mid-size companies connect AI and LLMs to the data that actually matters. MSc Data Science & Marketing Analytics from Erasmus University Rotterdam.

## About

Stijn de Ruijter is an independent consultant who works at the intersection of data engineering, analytics strategy, and AI integration. He starts with the business problem, not the technology. Pragmatic about what gets built — if a spreadsheet solves the problem, he won't build a pipeline.

He works best embedded in teams with short feedback loops and direct communication. Most useful when work crosses boundaries: data, commercial systems, marketing, ops.

- [About page](https://stijnderuijter.nl/about): Full bio, how he works, background, what he does and doesn't do
- [Contact](https://stijnderuijter.nl/contact): Book a free intro call

## Services

- Data analytics strategy
- Data modeling & engineering
- AI/LLM integration and prompt engineering at scale
- Lead attribution modeling
- Commercial data infrastructure (CRM, marketing platforms)
- Cross-team data quality

## Selected Projects

- [Reg4U](https://stijnderuijter.nl/work): Optimized LLM pipelines for a healthcare AI startup — same quality, lower cost, switchable models (2025–2026)
- [CLS Healthcare](https://stijnderuijter.nl/work): Built dashboards and integrations for better marketing attribution (2024–2025)
- [HalloStroom](https://stijnderuijter.nl/work): Built the lead attribution model from scratch for a Dutch energy company — 4 years, full-stack ownership (2021–2025)
- [Rockit.](https://stijnderuijter.nl/work): Co-built a real-time call transcription platform with AI summarization, sentiment analysis, and a transcript chatbot (2023–2025)
- [ABN AMRO](https://stijnderuijter.nl/work): Designed a data modeling framework for domain datasets at one of the Netherlands' largest banks (2022–2023)
- [jiggr](https://stijnderuijter.nl/work): Data engineering on GCP — pipelines, PostgreSQL, cloud infrastructure (2023)

## Earlier Experience

- Allianz — Data Analyst (2019–2020)
- Deloitte Nederland — Data Analyst (2018)
- Capgemini — Data Analyst Intern (2016)

## Education

- MSc Data Science & Marketing Analytics — Erasmus University Rotterdam

## Links

- [Website](https://stijnderuijter.nl)
- [LinkedIn](https://www.linkedin.com/in/stijnderuijter)
- [Upwork](https://www.upwork.com/freelancers/~01a485a52a45d0d853)
- [Full project details](https://stijnderuijter.nl/work)

## Writing

- [Evals zijn de echte moat](https://stijnderuijter.nl/writing/evals-zijn-de-echte-moat) (Dutch, April 2026): Why an eval set — not your prompt — is the real competitive advantage of an LLM product. Includes a practical example from healthcare AI (Reg4U) using golden datasets, F2 metrics, and cost-aware model routing.