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Available for senior & principal roles

Senior Software
Engineer.
Still building.

Full-stack architect and engineer with three decades of proven experience delivering scalable, high-performance systems. From bare-metal to the cloud, from monolith to microservices — I've built it, shipped it, and maintained it.

30+ Years Experience
200+ Projects Shipped
15+ Industries Served
8 Tech Stacks Mastered
full-stack backend cloud APIs devops arch
🏗️
Specialty
System Architecture
Track Record
99.9% Uptime Delivered

Three decades of
engineering excellence.

I've spent 30 years doing the one thing that never gets old: solving hard problems with well-crafted software. I started writing code when the web was barely a concept, and I've evolved with every major shift in the industry — from client-server to cloud-native, from procedural to functional and object-oriented, from bare-metal deployments to containerized microservices at scale.

I'm equally at home designing a high-throughput data pipeline, architecting a distributed system, and shipping a polished front-end. I believe clean code, strong tests, and simple systems are the foundation of everything that lasts — and I bring that discipline to every project I touch.

I've worked across startups, enterprises, and regulated industries — building things from scratch and untangling decades of technical debt. I mentor teams, lead architecture decisions, and stay close to the code. That's where the real work gets done.

🏗️
System Architecture & Design Patterns
🎯
Precision Problem-Solving Under Pressure
Performance Optimization at Scale
🧪
Test-Driven & Quality-First Development
🤝
Technical Leadership & Team Mentorship
30+
Years of Production Engineering
Spanning every major technology era from the mid-90s to today's cloud-native landscape.
200+
Projects Shipped
End-to-end, across every layer of the stack.
15+
Industries
Fintech, healthcare, logistics, e-commerce, and more.
Full-Stack by design.
Not by accident.
Deep expertise in both back-end engineering and front-end craft means I can own decisions across the entire system — and communicate clearly with any team.

Built on a broad,
deep foundation.

Three decades means I've not just learned these technologies — I've watched them evolve, and adapted with them.

⚙️
Back-End Development
C# / .NET Node.js Python Java Go REST APIs GraphQL gRPC SQL Server PostgreSQL MongoDB Redis Message Queues Entity Framework
🎨
Front-End Development
TypeScript React Next.js Vue HTML5 / CSS3 Tailwind CSS Responsive Design Accessibility Web Performance State Management PWA
🏗️
Architecture & Systems Design
Microservices Event-Driven Domain-Driven Design CQRS / Event Sourcing Clean Architecture SOA API Gateway High Availability Distributed Systems
☁️
Cloud & DevOps
Azure AWS GCP Docker Kubernetes CI/CD GitHub Actions Azure DevOps Terraform Monitoring & Observability
🔒
Quality & Security
TDD / BDD Unit Testing Integration Testing E2E Testing Code Review OWASP OAuth / OIDC Performance Profiling SOLID Principles
🤝
Leadership & Soft Skills
Technical Mentorship Architecture Reviews Stakeholder Communication Agile / Scrum Cross-Team Collaboration Technical Writing Hiring & Interviews

I don't just write code.
I solve the right problems.

After 30 years, the biggest difference between a good engineer and a great one isn't technical — it's judgment. Knowing when to build, when to buy, when to simplify, and when to push back. That's what I bring on day one. Technical depth paired with the clarity to communicate it, and the experience to act on it.
🧱
Scalable Architecture
Systems designed to grow with the business — not refactored from scratch six months after launch.
Full-Stack Ownership
End-to-end expertise means fewer handoffs, faster delivery, and one person who can see the whole picture.
🛡️
Long-Term Reliability
Code that's maintainable, testable, and legible to the next engineer. I build for the team that comes after.
🎓
Technical Leadership
I make teams better — through code review, mentorship, architecture guidance, and honest technical direction.
🔄
Modernization Expertise
I've refactored legacy systems that hadn't been touched in a decade — safely, incrementally, and without the drama.

A track record that
speaks for itself.

Three decades of evolving technologies, growing responsibilities, and consistent delivery.

💼
Principal Software Engineer
Enterprise Technology Leader
2019 – Present

Lead architect for a distributed platform serving millions of daily active users. Redesigned the core data pipeline from a fragile monolith to a horizontally scalable event-driven system. Established engineering standards, led a team of 12, and drove adoption of DDD and clean architecture principles across multiple product lines.

↑ 4× Throughput ↓ 60% Infra Cost 99.97% Uptime SLA
C# .NET 8 TypeScript/React Azure Kubernetes SQL Server Redis Event Hub
🚀
Senior Full-Stack Engineer
High-Growth Fintech
2013 – 2019

Core engineer on a payments platform processing $2B+ in annual transactions. Owned the API layer, security architecture, and front-end dashboard used by 50,000+ merchants. Led the migration from a legacy stack to a modern cloud-native architecture with zero downtime.

$2B+ Transactions ↓ 80% API Latency Zero Downtime Migration
C# ASP.NET React Node.js AWS PostgreSQL Stripe API
🏥
Lead Software Engineer
Healthcare Technology Firm
2006 – 2013

Led development of a HIPAA-compliant patient management system used by 300+ clinics nationwide. Built the data integration layer that synchronized records across legacy EHR systems and a modern API-driven platform. Managed a 6-person engineering team and drove code quality initiatives that reduced production incidents by 70%.

300+ Clinics ↓ 70% Incidents HIPAA Compliant
C# .NET SQL Server HL7 / FHIR WCF WPF
🌐
Software Engineer → Senior Engineer
Regional Technology Consultancy
1998 – 2006

Delivered end-to-end solutions across a diverse client portfolio spanning logistics, retail, and government. Grew from individual contributor to leading client engagements and owning technical delivery. Deep experience in relational database design, n-tier architectures, and early web application development during the formative years of the public internet.

ASP / ASP.NET VB.NET SQL Server Oracle COM/DCOM
💡
Junior Developer → Developer
Early Career
1994 – 1998

Started writing code professionally before the commercial web existed. Built desktop applications, data entry systems, and early client-server architectures. Developed the discipline and fundamentals that still underpin my engineering approach today.

C/C++ Visual Basic Delphi FoxPro TCP/IP Networking

Selected projects.

Real problems. Real solutions. Measurable outcomes.

Real-Time Analytics Platform
Challenge

Legacy batch-reporting system caused 12–24 hour data delays, blocking business decisions and frustrating enterprise clients.

Solution

Designed and built an event-driven streaming pipeline ingesting 50M+ events/day with sub-second dashboard latency using Azure Event Hub, Stream Analytics, and a React-based dashboard.

Dashboard latency dropped from 18 hours to under 2 seconds. Client retention improved 34%.
C# .NET Azure Event Hub TypeScript React CosmosDB
🔄
Legacy ERP Modernization
Challenge

20-year-old ERP system on a deprecated stack, with no tests, no documentation, and a team afraid to touch it.

Solution

Led a 3-year incremental modernization using the strangler fig pattern — extracting modules into microservices while keeping production running continuously throughout. TDD from day one.

Full modernization with zero production outages. 92% test coverage on all new modules. Deploy frequency 10× faster.
C# .NET 8 SQL Server Docker Kubernetes xUnit
🔒
Multi-Tenant SaaS API Platform
Challenge

Single-tenant monolith unable to onboard new enterprise clients without custom deployments — killing growth.

Solution

Architected a multi-tenant API platform with row-level security, tenant isolation, OAuth 2.0 authentication, and a self-service developer portal — all without touching the core business logic.

Onboarding time dropped from 3 weeks to 2 days. Platform grew to 80+ enterprise tenants in 18 months.
C# ASP.NET Core OAuth 2.0 PostgreSQL Redis React
🏥
HIPAA-Compliant Patient Portal
Challenge

Healthcare provider needed a patient-facing web portal that integrated with 5 legacy EHR systems without a shared API standard.

Solution

Built an abstraction layer and unified GraphQL API over FHIR-mapped data, with end-to-end encryption, audit logging, and a WCAG 2.1 AA-compliant React front-end.

300,000+ patients onboarded in year one. 98% satisfaction score. Passed HIPAA audit without findings.
C# .NET GraphQL FHIR / HL7 React Azure
📦
High-Volume Order Processing Engine
Challenge

E-commerce platform's order system buckled under Black Friday traffic, causing lost orders and angry customers.

Solution

Rebuilt the order pipeline as an async, message-driven architecture with idempotent handlers, dead-letter queues, and auto-scaling workers. Load tested to 10× peak capacity.

Handled 12× peak load flawlessly on next Black Friday. Zero lost orders. Zero P1 incidents.
C# .NET RabbitMQ SQL Server Docker Polly
🤖
AI-Augmented Document Platform
Challenge

Legal firm managing 500K+ documents with no intelligent search — employees spent hours finding precedents manually.

Solution

Built a document intelligence platform integrating vector search and LLM summarization with the existing document management system, wrapped in a clean React UI with semantic query support.

Search time reduced from hours to seconds. Associates recovered an average of 6 hours per week.
C# .NET Azure OpenAI Vector DB TypeScript React

What people
say about working with me.

"

Carlos has an extraordinary ability to take a vague problem, ask the right three questions, and come back with an architecture that's both elegant and practical. He's the kind of engineer who makes everyone around him better — and the systems he builds still work flawlessly years later.

MR
Michael R.
VP of Engineering, Fintech Platform
"

In 20 years of managing engineering teams, I've met very few people with Carlos's combination of technical depth and communication clarity. He's as comfortable presenting architecture tradeoffs to the board as he is reviewing a PR. A rare find at any level.

SL
Sarah L.
CTO, Healthcare Technology
"

We brought Carlos in to rescue a failing legacy migration. Within two weeks he had diagnosed the root causes, proposed a path forward, and started shipping fixes. The system he rebuilt now processes 10× the load with a fraction of the incidents. He's simply exceptional.

AK
Andrew K.
Director of Technology, E-Commerce

Ready to build
something great?

Whether you have a specific project in mind or just want to explore how I might help — I'd like to hear from you.

✉️
Email
carlos.sosa.us@gmail.com
📍
Location
Available Remotely & On-Site
⏱️
Response Time
Typically within 24 hours
Connect