Guido is available for hire
Hire GuidoGuido Daniel Russo Castagna
Verified Expert in Engineering
Software Developer
Valencia, Spain
Toptal member since March 3, 2026
Bio
Guido is a technical lead with 8+ years of experience architecting scalable, cloud-native solutions in healthcare, fintech, and industrial analytics. Specializing in .NET/C# and Azure infrastructure, he's delivered high-availability platforms that handle millions of daily transactions with over 99.9% uptime. As a Microsoft Certified Azure Developer and an adjunct professor, Guido blends deep technical expertise with strong leadership skills, adeptly mentoring teams and driving optimizations.
Portfolio
Agos
C#, Azure, AWS IoT, Business, React, Angular 6, .NET, .NET Core...
Endava
C#.NET, Azure, AWS IoT, Google Cloud Platform (GCP), Angular 6, Agile...
Southworks
C#.NET, Azure, React, JavaScript, .NET, .NET Core, Redis, Architecture...
Experience
- C#.NET - 8 years
- C# - 8 years
- SQL - 7 years
- Azure - 5 years
- Leadership - 4 years
- AWS IoT - 3 years
- Google Cloud Platform (GCP) - 3 years
- Business - 2 years
Preferred Environment
Windows, Azure, C#.NET, Slack, Jira, .NET
The most amazing...
...thing I've built is the Microsoft Email Orchestrator, delivering 600 million emails monthly with a 99.95% success rate and intelligent anti-spam controls.
Work Experience
Engineering Consultant and Business Development Manager
2022 - PRESENT
Agos
- Led technical strategy and architecture for 3+ simultaneous enterprise projects in healthcare, fintech, and industrial analytics, coordinating distributed teams of 15+ engineers, QA, DevOps, and product managers to successfully deliver on schedule.
- Architected a high-availability cloud platform handling millions of daily transactions with 99.9%+ uptime, implementing auto-scaling strategies and infrastructure optimization that reduced Azure cloud spend by 35%.
- Designed and delivered HIPAA-compliant healthcare back-end systems using .NET Core, Azure SQL, and Azure Key Vault, successfully passing security audits and achieving regulatory approval for production deployment.
- Mentored 10+ engineers on cloud architecture, design patterns, and Azure best practices, improving team velocity by 40% and reducing production incidents by 50% through structured code reviews and knowledge-sharing sessions.
- Established technical governance framework, including architecture review boards and DevOps standards, reducing deployment failures by 70% and accelerating time-to-market by 3 weeks per release cycle.
- Built an offline-first mobile application using Swift for industrial construction scoring, implementing efficient data synchronization and conflict resolution for limited-connectivity environments, supporting 500+ field workers.
- Collaborated with C-level executives and Fortune 500 client stakeholders to translate business objectives into technical roadmaps, mitigating delivery risks and ensuring alignment between technical architecture and strategic goals.
Technologies: C#, Azure, AWS IoT, Business, React, Angular 6, .NET, .NET Core, Event-driven Systems, Architecture, Microsoft SQL Server, Azure Cosmos DB, Microsoft Entra, Azure SQL, Azure Functions, Blob Storage, Azure App Service, Azure DevOps Services, Large Language Models (LLMs), AI Automation
Senior Software Engineer and Technical Lead
2021 - 2022
Endava
- Coordinated technical delivery across 4+ concurrent enterprise projects for Fortune 500 clients in payments, real estate, insurance, and healthcare, ensuring on-time delivery and maintaining 95%+ client satisfaction scores.
- Led architecture design sessions for a payment processing platform handling $10+ million monthly transactions, implementing microservices patterns and security controls that achieved PCI-DSS compliance and zero security incidents.
- Built and led an internal .NET engineering community of 30+ engineers across 8 global teams, establishing coding standards and best practices that improved code quality metrics by 40% and reduced technical debt.
- Mentored 5+ mid-level engineers through structured 1-on-1s and code reviews, resulting in 3 promotions to senior roles and improving team velocity by 35% through knowledge transfer and skill development.
- Implemented CI/CD pipelines using Azure DevOps across multiple projects, reducing deployment time by 70% and enabling multiple daily zero-downtime releases with automated testing and rollback capabilities.
Technologies: C#.NET, Azure, AWS IoT, Google Cloud Platform (GCP), Angular 6, Agile, Team Guidance, Leadership, JavaScript, .NET, Python, .NET Core, Redis, Event-driven Systems, Architecture, Microsoft SQL Server, Azure Cosmos DB, Microsoft Entra, Azure SQL, Azure Functions, Blob Storage, Azure App Service, Azure DevOps Services, Large Language Models (LLMs)
Software Engineer
2019 - 2021
Southworks
- Developed Microsoft Email Orchestrator back-end services, delivering 600+ million emails monthly with intelligent throttling and anti-spam controls, achieving a 99.95% delivery success rate.
- Designed and implemented a scalable email queue management system using Azure Service Bus and .NET Core, handling peak loads of 25+ million emails per day with zero downtime.
- Contributed to the Azure cohort management platform supporting A/B testing and feature rollout for millions of users, enabling data-driven product decisions across Microsoft services.
- Maintained over 90% unit test coverage across mission-critical microservices, ensuring SLA commitments and reducing production incidents by 45% through comprehensive testing strategies.
- Collaborated with Microsoft engineering teams in a distributed environment, participating in code reviews and architecture discussions that improved system reliability and performance by 30%.
Technologies: C#.NET, Azure, React, JavaScript, .NET, .NET Core, Redis, Architecture, Microsoft SQL Server, Docker, Azure Cosmos DB, Microsoft Entra, Azure SQL, Azure Functions, Azure App Service, Azure DevOps Services
Software Engineer
2017 - 2019
Boston Insurance
- Built an enterprise insurance producer management application using .NET Framework and SQL Server, improving onboarding efficiency by 40% through automated validation and streamlined workflows.
- Implemented a data integrity validation layer that reduced data entry errors by 35%, ensuring compliance with regulatory requirements and improving data quality across the platform.
- Troubleshot and resolved 50+ production incidents within SLA timeframes, maintaining 99% system availability and minimizing business disruption for insurance operations.
- Refactored legacy codebase modules, reducing technical debt and improving application performance by 25%, resulting in faster response times and enhanced user experience.
- Collaborated with cross-functional teams of 8+ members, including business analysts and QA engineers, to deliver 15+ features on schedule, meeting sprint commitments and business requirements.
Technologies: C#.NET, Azure, SQL, HTML, CSS5, JavaScript, .NET, Microsoft SQL Server, Azure SQL, Desktop App Development
Experience
High-scale Email Infrastructure
Developed Microsoft Email Orchestrator processing 600+ million emails monthly using C# and Azure Services. I built intelligent throttling and retry mechanisms, achieving 99.95% delivery success while reducing infrastructure costs by 28%. I also contributed to distributed configuration services supporting 50+ million users.
Education
2016 - 2022
Bachelor's Degree in Computer Engineering
UADE Business School - Buenos Aires, Argentina
Certifications
NOVEMBER 2020 - PRESENT
Microsoft Azure Data Engineer Associate
Microsoft
Skills
Libraries/APIs
React
Tools
Slack, Jira, Azure App Service, Azure DevOps Services
Languages
C#.NET, SQL, C#, C++, JavaScript, Assembler, HTML, Python
Frameworks
.NET, .NET Core, Angular 6
Platforms
Windows, Azure, Azure Functions, AWS IoT, Google Cloud Platform (GCP), Docker
Storage
Azure Cosmos DB, Azure SQL, Redis, Microsoft SQL Server
Paradigms
Desktop App Development, Agile
Other
MathScript, Architecture, Robotics, System Design, Software Architecture, Leadership, Business, Microsoft Entra, Blob Storage, Event-driven Systems, Large Language Models (LLMs), Microcontrollers, Software Engineering, CSS5, Team Guidance, AI Automation
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