Mateus Lazarus

Nubank — São Paulo, Brazil

• Chosen as one of the people to start the new Reconciliation team inside Global Platforms and Core Banking area, responsible for all core banking flows of clearing, chargeback, fee collections, and settlement related to the card system network (Mastercard), providing accounting data of all liabilities across all countries Nubank operates in (BR, CO, MX, US) for SAP.
• Improved the accuracy of the reconciliation platform, reducing annual financial exposure from approximately USD 240M to less than USD 12K across all countries within 1 year.
• Proactively suggested, applied, and gathered feedback to improve team processes, achieving a weekly average of 6-8 PRs per engineer in the team and less than 1 day to go through review.
• Acted as a key person for multiple Mastercard and Regulators Mandates to assure the business did not take any financial fees or exposure.
• Led the migration of 2 legacy services handling +100M customer transactions daily to a new platform, achieving 100% observability, refactoring model design, accelerating feature deliveries, and enabling near real-time automated monitoring of key business metrics.
• Owned the discovery of the initiative to expand the reconciliation platform to support debit products across every country where Nubank operates, defining the opportunity, business scope, and cross-country requirements.
• Handled multiple stakeholders, creating work agreements and a standardized way to communicate through mandates and platform integrations.
• Conducted an internal interview process with 16 people (mostly engineers) to define personas and understand the drivers behind high-performance AI users vs. barriers for lower-engagement users.
• Partnered with the Senior Chief of Staff to improve Business Area AI engagement from 33% to 86% by defining standardized study paths and tool setups for ICs, hosting hackathons, and addressing key insights.
• Authored the company's largest AI MCP guides across over 10 internal guide pages, reaching +3,350 people inside the company and generating +10,000 views.

Stone Co. — São Paulo, Brazil

• Working on high-scale financial applications handling 12B+ requests annually while maintaining 99.95%+ uptime.
• Maintaining exceptional code quality with more than 95% code coverage across all projects.
• Architecting and implementing distributed systems for high-demand, high-reliability workloads in the financial sector.
• Implementing microservices environments using Domain-Driven Design (DDD) and Behavior-Driven Design (BDD) practices.
• Leading migration projects from SpecFlow to Reqnroll for BDD testing frameworks.
• Implementing automated testing strategies using SpecFlow, Reqnroll, and Playwright for functional testing.
• Contributing to DevOps initiatives with CI/CD pipelines using GitHub Actions and Azure Pipeline.
• Managing observability and monitoring using New Relic, Pingdom, Datadog, Grafana Loki, and Splunk.
• Working with data lake solutions using Google BigQuery for analytics and reporting.
• Implementing Infrastructure as Code (IaC) using Terraform for cloud resource management.

Freelance / Independent Contractor

• Contributed to projects characterized by low maintenance requirements and substantial impact on fostering customer loyalty.
• Utilized PHP, Relational Databases, and JavaScript, laying a solid foundation for creating tangible value for both the business and its clientele.
• Played a pivotal role in enhancing operations for Atenas Fit Oficial, a local enterprise with over a decade of presence in the fitness and health industry — optimizing CRM services, fortifying entrance security protocols, and implementing measures to monitor disengaged and unpaid customers.