David Marcos

• Built modular React + TypeScript frontends and reusable UI components for analyst workflows. • Developed advanced D3.js force graph visualizations for investigative analysis (zoom/pan, filtering, highlights). • Designed and secured backend APIs using Flask, PostgreSQL, and graph DB integrations with OIDC + JWT + RBAC. • Improved system performance through ORM optimization, indexing, caching, and query tuning. • Implemented unit tests (pytest) and UI tests (Selenium) integrated into CI/CD. • Containerized and deployed systems across DEV/QA/PROD using Azure DevOps. • Implemented platform-wide i18n with locale routing and translation workflows.

In Citymapper I worked mainly on integrating and maintaining data pipelines for real time transport data, mainly related to public transport in different cities and countries. I have also had to work on infraestrucure as a code, deployments and creating APIs. I have worked with Python (flask, pandas...), AWS (EC2, Lambda, Cloudwatch, DynamoDB...), and Grafana/InfluxDB for reporting, and Docker.

At Newtral.es, I worked in a variety of projects, from tools that help journalists on their daily work, to data analysis and visualization for data journalism projects, where I was able to work with journalists. This work was related to fighting misinformation in Spain. I developed APIs for internal tools using Flask and FastAPI on Python. I also collaborated with the ML team, where I used libraries like Pandas and Scipy. My work was related to the data pipelines used for the models, and deploying models as APIs.