Lucerne

I’m Marcos Messer. I build core systems and explore what’s next in AI.

Principal Engineer and VP of AI at crowdhouse in Zürich. I shape technical direction, write a substantial share of the code, and turn new AI capabilities into working software.

Lucerne 00:00building AI agent access at crowdhouselast active Nov 4

6,212 contributions in the last year

Selected projects

cold.global

An open-access research platform that helps legal scholars and practitioners compare how jurisdictions determine which law applies. I took over as sole engineer when the original team moved on, redesigned the site and comparison tools, and cut homepage load time (LCP) from 2.9 seconds to 0.2 seconds.

I also built an AI case analyser that extracts choice-of-law data from court decisions. It began as a standalone prototype and now runs within the platform.

Nuxt · Vue · TypeScript · Python · FastAPI · PostgreSQL · OpenAI · Azure · Cloudflare

Ledger

Side project · iPhone, iPad & Mac

A private household finance app for iPhone, iPad, and Mac, in daily use through TestFlight. It brings together expenses, budgets, investments, and savings, with offline recording and sync across the household.

Apple Pay transactions arrive as drafts through Shortcuts; receipts, Swiss QR-bills, and statements fill in the details. Each household has its own database, and forecasts stay separate from recorded spending.

Swift · SwiftUI · SwiftData · Supabase · PostgreSQL · TypeScript

agathabrandao.com

My wife's academic website, bringing together her research in transnational law, publications, and events in four languages. I built and maintain it, with a focus on fast pages and straightforward publishing. It scores 100 on PageSpeed on both mobile and desktop.

Next.js · TypeScript · Tailwind CSS · DatoCMS · GraphQL · Vercel

patrimoniosolar.com

The website for my brother's solar energy company in Brazil, with services, practical advice, and quote requests. As its sole developer, I moved it from Hugo to Astro and continue to improve its speed, usability, and search visibility.

Astro · Tailwind CSS · Cloudflare

formacaoglobal.com

My wife's study-abroad advisory, sharing scholarships, mentoring, and stories from past students. I've built and maintained the site since 2016 as it grew to thousands of visits. Recent work includes a scholarship atlas and lighter, faster pages.

Hugo · Cloudinary · Cloudflare

Work

Principal Engineer—crowdhouse AG

Apr 2026 — now

Technical direction, a large share of the code, and VP of AI. Built accounts payable end to end — AI invoice extraction, duplicate and creditor checks, role-based approval chains and budgets, delivery to Abacus — as the first piece of a property-management DMS. Added an MCP server that lets AI agents query the platform, with auditable writes and PII redaction. Keeps the team fast: migration and architecture checks, agent skills that encode the domain rules, and main-branch CI p90 cut from 35 to 20 minutes.

TypeScript · Next.js · NestJS · Python · AWS · Terraform · MCP

Engineering Manager—crowdhouse AG / Driven AG

Dec 2023 — Apr 2026

Planning and delivery for a team of twenty — developers, product, design, and business analysts — and Director of AI, still shipping across two products. At crowdhouse: a Python AI service with RAG and spreadsheet extraction checked against contract data, an auditable asset log with tasks and comments, and the DDD base classes and ADRs the team builds its aggregates on. At Driven: data rooms, client-side vault encryption, and subscription tiers. Reduced frontend builds from 12 minutes to 6½.

TypeScript · Next.js · NestJS · Python · FastAPI · AWS

Tech Lead—Driven AG / crowdhouse AG

Jan 2023 — Dec 2023

Architecture, standards, and the guardrails that let a cross-functional team move fast: role guards enforced on every resolver, one lint and format rule set across 590 files, pre-commit hooks, typed test mocks, sharded CI, and the move from react-scripts and Jest to Vite and Vitest. Per-PR CI in five minutes across 5,000 unit and 2,000 integration tests. Shipped the marketplace end to end — listings, negotiations, payments — and usage quotas. The monorepo's top committer, about twice the next, with some 360 reviews that year.

TypeScript · React · NestJS · GraphQL · Vite · AWS · Terraform

Senior Software Engineer—Driven AG / crowdhouse AG

Dec 2021 — Dec 2022

Full-stack TypeScript on a vehicle-ownership platform — React, NestJS, GraphQL, and AWS as code with Terraform. Laid the foundations the team still builds on: the end-to-end suite from zero, release automation with separate staging and production deploys, per-PR test selection, and a security-first GraphQL schema. Shipped the vehicle vault, image pipeline, valuations, and log-book imports.

TypeScript · React · NestJS · GraphQL · AWS · Terraform

Software Engineer—EF Education First / EF Kids & Teens

May 2019 — Nov 2021

Sole developer on a ten-person recruitment team — Next.js and Gatsby sites on Storyblok, and a Salesforce funnel recruiting teachers for the US, UK, Malta, China, and South Africa. Part-time on a second Lucerne team's classroom platform: React frontend, Go backend.

Next.js · Gatsby · Go · Storyblok · Salesforce · AWS

Software Engineer—Tribunal Regional do Trabalho 17a Região - TRT-ES

Apr 2014 — May 2019

Court systems in C#/.NET for a regional labor court — 800 internal users, thousands more external. OData APIs, SOAP services, Nintex workflows, and portal features; SharePoint migrations from 2013 through 2019, several terabytes, the last done remotely from Switzerland.

C# · VB.NET · ASP.NET · WPF · UWP · SharePoint · Nintex · Oracle · MSSQL

About

I grew up in Brazil and have been writing software for over a decade. My work has taken me from systems for a regional labour court to teacher recruitment at EF Education First, then vehicle ownership and property management at Driven and crowdhouse.

I take on the architecture and much of the implementation. At crowdhouse, that includes building accounts payable end to end, integrating AI into the platform, and developing the domain foundations and checks the team relies on. I care about clear plans, honest feedback, and holding my own work to the standard I ask of others.

As VP of AI, I stay close to emerging models and tools, experimenting with what they can do and where they can improve our products and how we build them.

Outside work, I maintain the Choice of Law Dataverse, build Ledger for our household finances, and keep my wife’s and my brother’s websites running. At home, a Synology NAS runs more services than any household needs.

Engineering Leadership

I've helped lead teams of up to twenty across engineering, product, design, and analysis while remaining a major contributor to the code. I design core systems and review the work that builds on them. Clear plans and written decisions give the team a shared direction.

Foundations for Teams

Shared architecture and reusable building blocks. I build domain models, architecture checks, and AI agent skills that capture project conventions and help the team apply them consistently.

CI/CD & Cloud

Less time waiting for feedback: frontend builds reduced from 12 minutes to 6½, and functional tests from 137 seconds to 22. Infrastructure and delivery on AWS with Terraform, Docker, and GitHub Actions.