# Guillermo Castro > Senior Software Engineer | Back-end Development, Cloud Solutions guillermo.castro@gmail.com | +528181623288 | Monterrey, Nuevo Leon, MX [LinkedIn](https://www.linkedin.com/in/javageek) | [Github](https://github.com/codegeek) Nearly 30 years of hands-on Java depth, paired with daily production use of AI tools to ship faster and modernize legacy systems. Built and scaled back-end platforms for major retail, e-commerce, and education brands; from Zappos' post-Amazon-acquisition integration work to Cengage Group's learning platform serving 16 million users, as both a direct hire and independent consultant. The Java expert and mentor every team turns to. ## Work ### [Owner, Fusivo LLC](https://fusivo.com) *2009-08 - Present* - Founded Fusivo LLC as a corp-to-corp consulting vehicle to contract with Savoir Technologies on back-end development engagements. - Delivered high-quality code solutions that improved client systems and processes, enhancing overall efficiency. - Currently maintained in a part-time capacity for billing administration and internal projects while employed full-time elsewhere. ### [Senior Software Development Engineer, Zillow](https://www.zillow.com) *2025-11 - 2026-08* - Worked with the communications platform team to coordinate, develop, and maintain services for sending all communication from Zillow to the clients using remote collaboration tools (Gitlab, Slack, JIRA, Confluence, Zoom). - Developed new system for sending push notifications to mobile devices (iOS, Android) using third party services (Urban Airship). - Migrated 3 services from legacy platforms and legacy code (Spring Boot upgrades, Kubernetes, Terraform). - Leveraged multiple AI resources (Claude Code, Cursor, Codex, Glean) daily to increase performance, including creating multiple skills and plugins for daily project tracking, and a knowledge base with Obsidian. - Maintained multiple services using observability and monitoring tools (CloudWatch, Datadog, Splunk, Grafana, Databricks) with Python scripting. ### [Senior Software Engineer II, Zeitview](https://zeitview.com) *2024-10 - 2025-08* Zeitview (formerly DroneBase) is an AI-powered inspection platform for critical infrastructure, active in 60+ countries. - Developed back-end software using Spring Boot for Asset Intelligence & Visualization, reducing manual review time by an estimated 15-20% for critical infrastructure inspections. - Designed and implemented an asset condition scoring system using Spring technologies, enhancing cloud-native deployment strategies. - Collaborated with remote teams through code reviews and pull requests, ensuring compliance with industry standards, using modern remote collaboration tools (Github, Slack, Google Meet, JIRA). - Leveraged AI coding tools like GitHub Copilot to streamline development processes and increase productivity. ### [Computer Systems Analyst, Savoir Technologies, Inc](https://www.savoirtech.com) *2009-10 - 2024-10* Nearly 15 years of continuous independent consulting, staffed through Savoir Technologies across successive client placements at Cengage Group, Office Depot, Ferguson, Manheim, and Zappos (each detailed separately below). ### [Software Consultant, Cengage Group](https://www.cengage.com) *2019-08 - 2024-03* Cengage Group serves roughly 16 million digital users annually across 100+ countries, reaching about 70% of U.S. higher-education institutions and K-12 school districts. - Developed and implemented an API integration for intra-corporate use using Spring Boot. - Designed and maintained a gateway system connecting multiple Learning Management Systems with Cengage Content Systems. - Utilized various APIs, including LTI Advantage, to enhance tool interoperability across platforms. ### [Software Consultant, Office Depot, LLC](https://www.officedepot.com) *2018-05 - 2019-06* - Designed and implemented microservices using Camel and Spring Boot for seamless enterprise integration. - Deployed applications on AWS and on-premises using Kubernetes, Jenkins, and Rancher. - Utilized Splunk, Dynatrace, and ELK for troubleshooting, enhancing system reliability and performance. ### [Software Consultant, Ferguson](https://www.ferguson.com) *2017-12 - 2018-04* Ferguson Enterprises is a multi-billion-dollar North American distributor of plumbing, HVAC, and water solutions. - Designed and implemented a microservices-oriented REST backend platform for e-commerce applications. - Utilized Docker and OpenShift for continuous development and integration, enhancing deployment efficiency. - Collaborated with cross-functional teams to ensure seamless integration of new features and technologies. - Contributed to Ferguson Enterprises' growth by improving system scalability and performance. ### [Director of Information Technology, Ella Paradis](https://www.ellaparadis.com) *2017-06 - 2017-11* - Engaged directly, independent of the Savoir Technologies consulting relationship, between client placements. - Directed a 2-developer team from an external contractor firm, providing comprehensive IT support and enhancing technology solutions for the e-commerce platform Magento under MySQL. - Designed a REST API microservices application, streamlining fulfillment, order management, and inventory tracking. ### [Software Consultant, Manheim](https://www.manheim.com) *2016-10 - 2016-12* Manheim, a Cox Automotive brand, is the world's largest wholesale used-vehicle marketplace, facilitating roughly $57 billion in annual transactions. - Development and support of multiple backend systems using Open-Source frameworks Apache Camel, Karaf, ActiveMQ, PostgreSQL. ### [Software Consultant, Zappos.com](https://www.zappos.com) *2009-10 - 2016-09* Zappos is a $1B+ online retailer carrying hundreds of brands, acquired by Amazon in 2009. - Implemented robust backend systems for Zappos using modern frameworks like Spring. - Established API connections to external systems including Stripe and AWS, enhancing operational efficiency. - Supported integration of Zappos' proprietary warehouse and inventory system ("Genghis") with Amazon's supply chain and fulfillment infrastructure following the 2009 acquisition, streamlining product categorization and warehouse management. ### [Software Consultant, LeapFrog Enterprises](https://www.leapfrog.com) *2008-01 - 2009-01* - Developed SOA-based services for the Leapfrog Connect application Leaning Path, enhancing user engagement and functionality. - Utilized Open Source frameworks such as Spring, Apache CXF, and Mule to streamline service integration. - Collaborated with cross-functional teams to optimize Oracle PL/SQL queries, improving data retrieval efficiency by 30%. ### Senior Developer / Software Consultant, Earlier Experience *1996-08 - 2007-12* Designed and developed enterprise Java (JEE), .NET, PHP, and Oracle/PL-SQL systems across six roles at Dextra Technologies, eMonterrey, FEMSA Comercio, IIDEA Solutions, Softtek, and H-E-B, spanning e-commerce platforms, ERP applications, and SOA integration for clients including Inktomi, Apple, Portal Software, GE Wind, and Citigroup. ## Education ### Monterrey Institute of Technology — B.S., Engineering Physics *1991-08 - 1996-06* - Physics Engineering - Electronics ## Skills ### AI-Assisted Development — Advanced GitHub Copilot, Claude Code, Cursor, Codex, Glean ### Programming Languages — Expert Java, Python ### Frameworks — Expert Spring, Spring Boot, Apache Camel ### Additional Languages & Frameworks — Familiar Kotlin, PHP, Quarkus, JEE, Bash ### Cloud & DevOps — Advanced Docker, Kubernetes, AWS, Terraform, Jenkins, OpenShift ### Observability — Advanced Splunk, Dynatrace, ELK Stack, Grafana, CloudWatch, Datadog, Databricks ### Databases — Advanced Oracle, MySQL, PostgreSQL ### Tools — Expert Git, Github, Gitlab, Intellij IDEA, Android Studio ## Languages - English — Fluent - Spanish — Native speaker ## Interests ### Software Technologies New technologies, Industry trends ### Gaming PC