Dennis S.

Full stack software engineer with 10 years of experience across web applications and backend systems, including native Windows software. Technical background in application architecture and API integration, with database design and performance engineering. Top Rated Plus on Upwork with 100% Job Success.

Specializing in AI engineering and practical implementation, including LLM integration and conversational voice systems. Experience with OpenAI and Claude, alongside Telnyx and Retell AI. Development scope covers custom SaaS platforms and internal business applications, from frontend interfaces and backend services through authentication and subscription billing. Full application delivery and integration into established codebases.

🧠 AI Engineering & Integration
OpenAI and Claude integration for custom applications and existing software. AI agents with tool calling, structured outputs and persistent conversation context. Prompt and tool definitions with schema validation and application permissions.

Streaming transcription and text to speech. Transcript translation, AI summarization and structured content generation. AI service integration across the API layer and data storage, with supporting application interfaces.

🎙️ Voice AI | Telnyx & Retell AI
Telnyx and Retell AI integration for websites and backend services. Direct OpenAI voice integration. Telnyx Voice API and Call Control, SIP connectivity and WebRTC.

WebSocket audio streaming and signed webhook handling. Voice session management, transcript persistence and backend tool integration. Relevant implementations include Clearline and Maître.

🌐 Full Stack & SaaS Development
SaaS applications and internal business software with React and TypeScript. Node.js and Python backend services. Database architecture, authentication and role based access. Dashboards and administration interfaces.

Stripe checkout and subscription billing, including customer portals and webhook processing. Usage limits and subscription access controls. Media uploads and protected content delivery. AWS, Docker deployment

🐍 APIs & Backend Systems
REST API development and third party service integration through authenticated endpoints and webhooks. Python and FastAPI services for data processing and workflow automation. Request validation, event handling and persistent application state.

Cloudflare Workers and Durable Objects, including service configuration and server side credential management. API troubleshooting and duplicate event handling across connected services.