Guillermo Castro

Skills

Experience

1. Owner · Fusivo LLC

   Aug 2009 — Present

   Remote

   • 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.

2. Senior Software Development Engineer · Zillow

   Nov 2025 — Aug 2026

   Remote

   • 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.

3. Senior Software Engineer II · Zeitview

   Oct 2024 — Aug 2025

   Remote

   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.

4. Computer Systems Analyst · Savoir Technologies, Inc

   Oct 2009 — Oct 2024

   Remote

   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).

5. Software Consultant · Cengage Group

   Aug 2019 — Mar 2024

   Remote

   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.

6. Software Consultant · Office Depot, LLC

   May 2018 — Jun 2019

   Boca Raton, FL

   • 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.

7. Software Consultant · Ferguson

   Dec 2017 — Apr 2018

   Newport News, VA - Remote

   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.

8. Director of Information Technology · Ella Paradis

   Jun 2017 — Nov 2017

   Miami, FL

   • 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.

9. Software Consultant · Manheim

   Oct 2016 — Dec 2016

   Atlanta, GA

   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.

10. Software Consultant · Zappos.com

    Oct 2009 — Sep 2016

    Las Vegas, NV

    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.

11. Software Consultant · LeapFrog Enterprises

    Jan 2008 — Jan 2009

    Emeryville, CA - Remote

    • 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%.

12. Senior Developer / Software Consultant · Earlier Experience

    Aug 1996 — Dec 2007

    Monterrey, Mexico

    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

Contact

Open to senior back-end and cloud engineering opportunities. Reach out directly or find me on the platforms below.