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Marshall Castillo
🇺🇸United States (UTC-08:00)
Created AtUpstaffer since January, 2026

Marshall Castillo — Full Stack Developer

Expertise in Full Stack Web (7.5 yr.), DevOps (5.0 yr.).

 Last verified on January, 2026

Bio Summary

I am a Senior Full Stack Developer with over 10 years of extensive and deep experience  designing, developing, and deploying high-performance web applications and enterprise-level platforms. My expertise spans the entire technology stack, allowing me to deliver robust, scalable, and maintainable solutions from concept to production.

Technical Skills

Programming LanguagesJavaScript
JavaScript FrameworksExpress, Node.js, React
Databases & Management Systems / ORMMongoDB
UI Frameworks, Libraries, and BrowsersCSS, HTML, XML
Amazon Web ServicesAWS Security Groups
Azure Cloud ServicesAzure DevOps
Google Cloud PlatformGCE
Methodologies, Paradigms and PatternsAgile, microservices
QA, Test Automation, SecurityAPI testing, JUnit
SDK / API and IntegrationsAPI testing
Deployment, CI/CD & AdministrationCI/CD
Soft SkillsCritical Thinking, Leadership
Virtualization, Containers and OrchestrationGCE
iOS Libraries and ToolsMDM
Project Management & AdministrationProject Management
UI/UX/WireframingResponsive Design
Version ControlSVN
Mail / Network Protocols / Data transferWebRTC
Other Technical SkillsOptimism, Public Relations, Teamwork

Work Experience

Freelancer, Tailored Marketing Strategies and Brand-Development Solutions

Duration: 06/2025 - Present
Summary:
  • Provided tailored marketing strategies and brand-development solutions to clients across tech, SaaS, and digital-product sectors after completing contract with Palo Alto Networks
  • Built and executed data-driven marketing campaigns that increased client acquisition rates by 25–40% depending on project scope
  • Improved brand positioning for early-stage companies, resulting in 15%+ growth in customer engagement within the first 90 days
  • Developed content and messaging frameworks that boosted lead-conversion rates by up to 30% for long-term clients
Responsibilities: Developed and executed marketing campaigns, improved brand positioning, created content and messaging frameworks to boost lead conversion and customer engagement.
Technologies: Marketing analytics tools, data-driven campaign platforms

Senior Full Stack Developer & Team Leader, High-Performance Scalable Web Solutions

Duration: 01/2023 - 06/2025
Summary:
  • Led a team of 6 developers, delivering high-performance, scalable web solutions that improved product stability and user satisfaction by 22% YoY
  • Architected and implemented full-stack features using React, Node
  • js, Express, and MongoDB, enhancing platform efficiency and reducing load times by 28%
  • Managed and optimized engineering resources and project timelines for initiatives exceeding $1
  • 2M+ in annual technical scope
  • Ensured consistent code quality and system reliability across 15+ services, reducing critical production issues by 17%
  • Collaborated with product, design, QA, and DevOps teams to deliver multi-region feature deployments with seamless integration and minimal downtime
Responsibilities: Team leadership, full-stack feature architecture and implementation, resource and timeline management, code quality assurance, cross-team collaboration for multi-region deployments.
Technologies: React, Node.js, Express, MongoDB

Full Stack Developer, Web Applications Development and Optimization

Duration: 05/2018 - 02/2023
Summary:
  • Led full-stack development of web applications using React, Node
  • js, Express, and MongoDB, improving platform performance and stability across multiple product teams
  • Designed and optimized scalable APIs and microservices, reducing server response times by 35% and improving system reliability
  • Built reusable UI components and frontend architectures that improved development speed by 25% across engineering teams
  • Ensured consistent brand application across all digital assets, increasing customer trust and reducing user experience inconsistencies by 30%
  • Implemented CI/CD pipelines, automated deployments, and cloud infrastructure improvements, decreasing deployment errors by 40%
  • Collaborated with cross-functional teams to deliver new features, contributing to a 20% increase in user adoption and engagement
  • Conducted performance tuning, debugging, and refactoring, reducing production issues by 30% and enhancing overall code quality
Responsibilities: Full-stack development, API and microservices design and optimization, UI component and frontend architecture development, brand consistency enforcement, CI/CD pipeline implementation, cloud infrastructure improvements, cross-team collaboration, performance tuning and debugging.
Technologies: React, Node.js, Express, MongoDB, CI/CD tools, cloud infrastructure

Junior Developer, Web Applications Development and Maintenance

Duration: 06/2016 - 04/2018
Summary:
  • Assisted in developing and maintaining web applications using JavaScript, HTML, CSS, and early React/Node fundamentals
  • Fixed bugs, improved UI components, and optimized front-end performance, reducing load times by 20% on key pages
  • Collaborated with senior developers on API integrations and backend improvements, contributing to 5+ successful product releases
  • Wrote automated test scripts that improved testing coverage by 25%, reducing recurring issues in production
  • Gained foundational experience in Agile workflows, Git version control, and full-stack development practices
Responsibilities: Bug fixing, UI component improvement, front-end performance optimization, API integration assistance, backend improvements, automated test script writing, Agile workflow participation.
Technologies: JavaScript, HTML, CSS, React (fundamentals), Node.js (fundamentals), Git

Education

  • Master of Computer Science
    Greenwood university, USA
    2015 - 2018

Certification

  • Advanced training in full-stack development, cloud computing, API design, database optimization, cybersecurity fundamentals, CI/CD automation, and modern JavaScript frameworks
    Completed advanced training to stay current with industry best practices.

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