Gabriel Schütz
Senior Software Engineer — Airport Revenue & Payment Systems
Six years building and running the software that turns an aircraft movement into money in the bank: fee calculation, matching, invoicing, collection, reconciliation and the accounting exports. One of three core developers of a German aviation SaaS used by 350+ airfields.
Available nowContracting company-to-company since 2021 · Brazil, GMT-3, 1–2h ahead of US Eastern: your whole business day is inside my working day.
Movement to cash: what I built
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€62.9M invoiced & collected
The approach-fee billing service I built in Node.js (v1 solo, 2021) for a national air-navigation services provider: movements in from the airports, MTOW-based fees per landing, fee notices out, collection behind it. All-time.
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~90% of movements matched to the paying party without a person
Early on I ran the monthly billing rounds by hand myself, and automated once the manual runs had taught me the real rules. Peak month: 10,856 movements, 363 fee notices, one operator running the round.
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Collections: a dunning service built from scratch
Escalation levels on a schedule, letters, fees, debtor blocking, a person approving every batch. The ledger is the single source of truth: a posted payment closes the case on its own. Bank-statement matching: ~80% of incoming customer payments match fully automatically, ~97% get a candidate.
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Airport-side billing and the pilot-facing portal
A large part of the airport management system, module by module: recurring charges, importers for debtors, aircraft and fee schedules, credit notes, quotes, aircraft ownership history. The operator portal, architected and led from 2020: card and SEPA payments with 3D Secure, self-onboarding without a login.
Books that agree: DATEV end to end, XRechnung / EN 16931 with a validator, an SAP FI interface taken solo to two production go-lives with written customer sign-offs, BMD and CEGID exports; the Stripe Connect layer re-architected into a central payment service.
How I work
A change is mine until it is live and quiet: I deployed it, watched it, and when it broke the ticket came to me. I was the escalation point for billing and accounting questions, diagnosed from the database and the logs.
Money in exact decimals. An idempotency key with a unique index behind it, because two processors will race. Every billed operation carries the evidence it was billed on, so a dispute is a lookup and not an argument. A migration is done when old and new produce the same invoices for a closed period, to the cent: that is how the billing domain left the legacy shop system, and how ~14,000 lines of boilerplate left the core backend behind a zero-diff harness.
Tests and CI as the back-pressure: in-process transactional acceptance tests, GitHub Actions, Playwright end to end, static analysis on every commit. AI tooling heavily and with verification: plan first, a second model cross-checks, tests, then human review on every pull request.
Stack
- Production: Node.js/Express, PHP/Laravel, SQL (MySQL/MariaDB: schema design, indexing, locking on billing tables), MongoDB
- Infra & testing: Docker, RabbitMQ, GitHub Actions (self-hosted runners), PHPUnit, Codeception, Jest, PHPStan, Playwright
- Payments & accounting: Stripe Connect, SEPA, bank-statement reconciliation, DATEV, SAP FI, XRechnung / EN 16931
I ramp quickly on new stacks and have taken over and modernized unfamiliar production codebases before.
Languages
- Portuguese
- English
- German
- French
Background
Remote from Brazil for five of the six years, as an independent contractor through my own company: a contract between the companies and a monthly invoice. The whole US business day is inside my working day.
B.Sc. Computer Science in progress (Uniritter, expected 2027); earlier coursework at TU Dresden. Before that, a technical high school for electronics, where the first programs were assembly and C on microcontrollers. ICYS Gold Medal (Stuttgart) and FEBRACE 2nd place for HAPTIKOS, a wearable for deafblind users; Weizmann Institute summer research scholarship.
Get in touch
References available: a signed reference from the aerops CEO, and written customer sign-offs on production go-lives.