Principal Full-Stack .NET / React / AI Architect

We are seeking a highly experienced Principal Full-Stack .NET / React / AI Architect to help lead the modernization and continued development of a complex enterprise technology environment.
This is a hands-on technical role for someone with deep experience across ASP.NET Web Forms, C#/.NET, React, SQL Server, APIs, payments, mobile applications, cloud infrastructure, and production AI systems.
Our environment includes established revenue-producing applications, modern React websites, React-based payment flows, iOS and Android applications, APIs, SQL Server databases, and new AI initiatives.
We need someone who can understand mature systems, make sound architectural decisions, and modernize them without disrupting customers, revenue, payments, SEO, uptime, or business operations.
Responsibilities
Architect, develop, and maintain enterprise applications across legacy and modern platforms
Work hands-on with ASP.NET Web Forms, .NET Framework, modern .NET, React, SQL Server, and REST APIs
Determine what should remain, be refactored, exposed through APIs, or rebuilt
Improve customer-facing React applications and payment flows
Architect backend services supporting iOS and Android applications
Build and integrate AI-powered features, agents, and automation
Improve scalability, security, reliability, observability, and performance
Review code and establish architecture and development standards
Troubleshoot complex production issues
Design secure third-party integrations
Guide incremental modernization without unnecessary rewrites
Communicate technical decisions clearly to business leadership
Required .NET Experience
Strong professional experience with:
C#
ASP.NET Web Forms
.NET Framework
Modern .NET / .NET Core
ASP.NET Core
Entity Framework / EF Core
SQL Server
REST APIs
IIS
Authentication and authorization
Role-based access control
Background processing
Logging and monitoring
Performance optimization
Automated testing
Git
CI/CD
Enterprise application architecture
ASP.NET Web Forms experience is required.
You must understand:
Web Forms page lifecycle
Master Pages
User Controls
Code-behind
ViewState
Session management
Postbacks
Server controls
Data binding
Legacy JavaScript and jQuery
IIS deployment
Production debugging
Safe legacy-code refactoring
Separating business logic from presentation
Gradual modernization through APIs and newer front ends
Required React Experience
Strong professional experience with:
React
TypeScript
JavaScript
Hooks
Component architecture
State management
REST API integration
Authentication and authorization
Complex forms and workflows
Dashboards
Responsive applications
Front-end performance
Error handling and monitoring
Secure backend communication
Technical SEO experience for public React websites is strongly preferred, including:
Core Web Vitals
Rendering strategies
Crawlability and indexability
Canonical URLs
Redirects
Structured data
SQL Server
You should have substantial experience with:
Database architecture
Complex queries
Stored procedures
Indexing
Query optimization
Transaction management
Data integrity
Database migrations
Large production databases
Reporting
Performance troubleshooting
Backup and recovery considerations
Payments
Payment-system experience is strongly preferred, including:
Payment gateway integrations
Secure React checkout architecture
Tokenization
One-time and recurring payments
Webhooks
Transaction validation
Failed-payment handling
Refunds and credits
Reconciliation
Idempotency and duplicate-transaction prevention
Fraud and abuse controls
PCI-conscious architecture
Server-side validation
Preventing client-side price manipulation
Financial transaction logging and audit trails
Mobile Applications
You do not need to be a dedicated native mobile developer, but you should understand backend systems supporting iOS and Android applications, including:
REST APIs
Token-based authentication
Refresh tokens
API versioning
Mobile session management
Mobile API security
Push notifications
Error and crash monitoring
Analytics
Backward compatibility
Release coordination
Experience with Swift, SwiftUI, Kotlin, React Native, or Flutter is a plus.
Required AI Experience
We are looking for meaningful production experience with AI systems, not simply use of ChatGPT or Copilot.
Relevant experience includes:
OpenAI APIs
Azure OpenAI
Anthropic or other major LLM providers
RAG
Vector databases
Embeddings
Semantic search
AI agents
Tool calling and function calling
Structured outputs
Prompt architecture
Context management
Workflow orchestration
Document ingestion and extraction
AI evaluation and testing
Guardrails
Hallucination mitigation
Permissions and access controls
Human approval workflows
Model routing
Cost and latency optimization
Production monitoring and observability
Experience with Semantic Kernel, Microsoft.Extensions.AI, Azure AI, LangChain, LangGraph, AutoGen, or similar technologies is valuable.
AI Agents and Enterprise Automation
We are particularly interested in candidates who understand how AI can safely interact with real enterprise systems.
Agents may:
Research information
Analyze documents
Extract structured data
Call internal and external APIs
Interact with databases
Assist customer service
Support internal operations
Automate repetitive workflows
Trigger approved enterprise actions
You should understand:
Permission boundaries
User and tool-level authorization
Human approval gates
Audit logs
Data-access controls
Prompt injection
Secure RAG architecture
Tenant isolation
Sensitive-data protection
Validation of AI-generated actions
Enterprise Architecture
You should be able to determine:
What should remain in Web Forms
What should be refactored
What should be exposed through APIs
What should move to React
What should be rebuilt in modern .NET
Where business logic should live
How mobile apps should interact with backend systems
Where AI can safely automate workflows
Where human approval is required
How to modernize without disrupting customers, revenue, payments, SEO, or uptime
We are not looking for someone who believes stable legacy systems should automatically be rewritten.
We want someone who understands intelligent, incremental modernization.
Third-Party Integrations
Relevant integrations may include:
Payment processors
OpenAI
Azure OpenAI
Intuit / QuickBooks
CRM platforms
Email and SMS providers
Analytics platforms
Identity verification services
Government or institutional systems
SaaS platforms
You should be comfortable with REST APIs, webhooks, OAuth, authentication, rate limits, retries, idempotency, monitoring, version changes, and secure credential management.
Experience maintaining older SOAP/XML integrations is also valuable.
Cloud and Infrastructure
Relevant experience includes:
Azure App Service
Azure Functions
Azure SQL
Azure Storage
Azure Service Bus
Azure Key Vault
Azure OpenAI
Azure AI services
Azure DevOps
Application Insights
AWS experience is also valuable.
You should understand IIS, deployments, environment configuration, secrets management, backups, disaster recovery, scalability, high availability, monitoring, logging, and rollback strategies.
Security
Strong understanding of:
Authentication and authorization
Role-based permissions
Least privilege
Secure API design
OWASP risks
SQL injection prevention
XSS
CSRF
Secure sessions
Secrets management
Encryption
Audit logging
Payment security
AI-specific security
Prompt injection
Data leakage
Tenant isolation
Ideal Candidate
The ideal candidate will likely have 10+ years of professional software development experience across multiple generations of Microsoft technology.
We are especially interested in candidates who have progressed through:
Legacy: ASP.NET Web Forms, .NET Framework, SQL Server, IIS
Modern: React, TypeScript, modern .NET, REST APIs, cloud architecture
AI: LLMs, RAG, AI agents, tool calling, and enterprise automation
You should think like an architect while remaining highly hands-on.
You should be able to:
Understand large codebases quickly
Architect new sy

Work arrangement
Yes