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I'm a Senior Software Engineer and SaaS Architect with 15+ years delivering production-grade platforms across FinTech, hospitality, healthcare, aviation, and AI. I've built 23+ live products as a solo full-stack developer, including multi-tenant SaaS systems, cross-platform Flutter apps, WhatsApp Business automation platforms, and AI chatbot integrations. I own the full stack: Flutter mobile, React/Next.js frontend, Node.js backend, PostgreSQL/Supabase data layer, and cloud deployments on Railway/Vercel. I collaborate with clients globally as a freelancer on Upwork and People Per Hour.…I'm a Senior Software Engineer and SaaS Architect with 15+ years delivering production-grade platforms across FinTech, hospitality, healthcare, aviation, and AI. I've built 23+ live products as a solo full-stack developer, including multi-tenant SaaS systems, cross-platform Flutter apps, WhatsApp Business automation platforms, and AI chatbot integrations. I own the full stack: Flutter mobile, React/Next.js frontend, Node.js backend, PostgreSQL/Supabase data layer, and cloud deployments on Railway/Vercel. I collaborate with clients globally as a freelancer on Upwork and People Per Hour.

Juan Diego Montero

Full Stack Developer, Web Developer, App Developer, +2

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I'm a Senior Software Engineer and SaaS Architect with 15+ years delivering production-grade platforms across FinTech, hospitality, healthcare, aviation, and AI. I've built 23+ live products as a solo full-stack developer, including multi-tenant SaaS systems, cross-platform Flutter apps, WhatsApp Business automation platforms, and AI chatbot integrations. I own the full stack: Flutter mobile, React/Next.js frontend, Node.js backend, PostgreSQL/Supabase data layer, and cloud deployments on Railway/Vercel. I collaborate with clients globally as a freelancer on Upwork and People Per Hour.…I'm a Senior Software Engineer and SaaS Architect with 15+ years delivering production-grade platforms across FinTech, hospitality, healthcare, aviation, and AI. I've built 23+ live products as a solo full-stack developer, including multi-tenant SaaS systems, cross-platform Flutter apps, WhatsApp Business automation platforms, and AI chatbot integrations. I own the full stack: Flutter mobile, React/Next.js frontend, Node.js backend, PostgreSQL/Supabase data layer, and cloud deployments on Railway/Vercel. I collaborate with clients globally as a freelancer on Upwork and People Per Hour.

Available to hire

I’m a Senior Software Engineer and SaaS Architect with 15+ years delivering production-grade platforms across FinTech, hospitality, healthcare, aviation, and AI. I’ve built 23+ live products as a solo full-stack developer, including multi-tenant SaaS systems, cross-platform Flutter apps, WhatsApp Business automation platforms, and AI chatbot integrations.

I own the full stack: Flutter mobile, React/Next.js frontend, Node.js backend, PostgreSQL/Supabase data layer, and cloud deployments on Railway/Vercel. I collaborate with clients globally as a freelancer on Upwork and People Per Hour.

Skills

Experience Level

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Language

English

Fluent

Spanish; Castilian

Fluent

Work Experience

Senior Software Engineer & SaaS Architect at Freelance (Upwork / People Per Hour)

January 1, 2009 - Present

Full ownership of architecture, backend, frontend, and mobile layers across 23+ production platforms. Built 9+ multi-tenant SaaS platforms with org-level data isolation, RBAC, and subscription billing. Developed REST APIs in Node.js/TypeScript with PostgreSQL and Supabase, including RLS-based tenant separation. Created 10+ Flutter mobile apps for iOS and Android with offline capabilities and location features. Integrated AI providers (OpenAI, Claude, Gemini) into workflow automation and chatbot products. Implemented WhatsApp Business Cloud API integration, webhook handling, and multi-step chatbot flows. Delivered Stripe Connect payment flows and multi-tier subscription billing. Deployed on Railway / Vercel with CI/CD pipelines.