Led Authorization's engineering execution for the Colombia debit launch, interfacing with the Fraud, Cards, and Debit teams — shipped 50% faster than the previous comparable market launch. Owned backend services processing ~1,700 transactions/second across debit and credit products in all markets, maintaining 99.97% uptime and sub-1-second authorization latency. Promoted to Senior Software Engineer following the Colombia launch; has remained an individual contributor since. Designed and built a real-time observability service for the authorization pipeline: captured raw Mastercard messages via Kafka before parsing, stored in DynamoDB, exposed via REST API — cut incident investigation time from next-day to immediate. Mentored a mid-level engineer through design and rollout. Early adopter and top user of an AI-assisted migration framework that converted legacy business rules into a new layered authorization architecture — the framework grew migration throughput from <20 rules/year to 33 rules in 6 months, with 10 more in progress. Built and operated backend microservices in Clojure for Nubank's payment authorization platform, processing transactions across Brazil, Mexico, Colombia, USA, and Switzerland for 100M+ customers. Cut infrastructure provisioning time from 21 days to 1 day by designing Infrastructure as Code with Terraform. Coordinated the gateway/boards team through PCI-DSS certification — delivered with zero pending items in 3 months. Stack: Clojure, Kafka, DynamoDB, AWS, Kubernetes, Terraform