Mario Arranz

Technical lead across several client engagements, covering the full lifecycle from architecture to delivery. Built LLM integrations and turned them into production-ready products. Owned end-to-end delivery on two concurrent projects, coordinating with client stakeholders and managing scope.

Five years on the payments core team at a SaaS billing platform. Designed and shipped the retry and recovery system that reduced failed payment volume by a significant margin. Built payment method integrations with multiple processors and led the migration of a high-traffic checkout flow to a new architecture.

Led a small backend team building a resilient, scalable API. Introduced structured observability with distributed tracing and cut p99 latency on the order flow by roughly half. Managed technical direction while staying hands-on with delivery.

Backend developer at a digital identity startup where security and privacy shaped every decision. Migrated key back-office services from Java to Go. Built internal tooling for identity verification workflows used across multiple regulated markets.

Joined as a full-stack developer at an early-stage ERP startup and moved into the PM role within a few months. Took the product from prototype to paying customers, handling technical delivery, client onboarding, and team coordination.

Lead developer on back-office platforms for travel industry clients, including Trenitalia. Delivered two projects end to end within tight deadlines, working directly with client technical teams.

Started as an intern while finishing university and stayed on for nearly three years. Built backend services for clients in the tourism sector. First professional exposure to production systems and real-world operational constraints.