About
Frontend‑focused full‑stack engineer with 10+ years building SaaS and enterprise applications. Specialized in UI architecture, reusable libraries, performance optimization, and experimentation at scale (200+ enterprise tests). Operates at staff level across mentoring, design/product collaboration, and roadmap influence. Founder of Mindcraftor.ai (2,000+ users) with expertise in AI workflows, SaaS billing, and product‑market validation.
I love building at the edge of complexity and usability — systems that are technically solid but also delightful to use. My career has taken me from leading experiments at Complex Networks, to federal-scale visualization at Peraton Labs, to founding SaaS startups like Mindcraftor. Along the way, I’ve learned that the best products don’t just solve problems — they create leverage.
Highlights / Proof
My Philosophy
I believe in shipping lean, testing aggressively, and learning faster than competitors. Whether in a corporate or startup setting, my focus is on clarity, scalability, and experimentation — because products that evolve quickly are the ones that win.
Beyond the Work
Outside of code, I’m a dad, a relentless tinkerer, and I love blending design with engineering. Whether it’s exploring AI workflows or teaching my daughter to problem-solve, I bring the same curiosity to everything I do.
FAQ
Who is Sangmin Lee?
I’m a full-stack engineer and SaaS founder with 10+ years of experience shipping production systems and leading experiments. I’ve worked across startups and enterprise environments, and I’m the founder of Mindcraftor and RankLabs. I specialize in Next.js/Node, experimentation, and performance-driven product delivery.
What kind of roles or work are you open to?
Senior full-stack engineering roles and select freelance engagements. Typical scopes: MVP builds, performance/UX improvements, experimentation frameworks, and AI-assisted workflows. I can lead end-to-end delivery or embed with existing teams.
What technologies do you specialize in?
TypeScript, Next.js/React, Node.js/Fastify, Postgres/Supabase, Tailwind, Redis, Stripe, and Framer Motion. I’m experienced with CRO/experimentation tools (Optimizely/Google Optimize patterns) and 3D geospatial visualization with CesiumJS in compliance-heavy environments.
What is Mindcraftor?
Mindcraftor is an AI SaaS for idea generation, validation, and autonomous CX workflows. It’s built with Next.js, Node.js, Supabase, and Stripe, and supports RAG-style flows with integrated analytics. It helps teams move from raw ideas to validated, testable product directions.
What is RankLabs?
RankLabs focuses on programmatic SEO and ranking systems, including Answer Engine Optimization (AEO). It combines data pipelines with AI-assisted insights to improve visibility across traditional SERPs and AI/answer engines.
What is “experimentation engineering”?
It’s the practice of building the technical rails for rapid, safe testing—client-side or server-side. I design testable UI patterns, measurement, guardrails, and analysis workflows so teams can learn fast without breaking core experiences, even in restricted environments like CDN-cached or WordPress stacks.
How do you approach performance and UX?
Start with baselines (Core Web Vitals), isolate regressions, and fix structural issues: bundle splitting, caching, prefetch strategies, and rendering patterns. I balance perceived performance with true latency reduction and ensure improvements are measurable, accessible, and resilient under real traffic.
Do you work with regulated or compliance-heavy teams?
Yes. I’ve delivered secure interactive 3D geospatial visualization and collaborated on federal compliance and accessibility aims. I design with least privilege, auditability, and progressive enhancement so features meet constraints without stalling product velocity.
Can you help validate a new SaaS idea?
Absolutely. I run lean validation: define the critical assumption, ship a minimal test surface, instrument it, and measure adoption/retention signals. I favor fast prototypes, realistic funnels, and clear kill/sustain criteria to avoid sunk-cost traps.
How do I start a project with you?
Email sangmlee23@gmail.com or use the Hire form on the site. Share goals, timeline, constraints, and any prior artifacts (briefs, designs, repos). I’ll propose scope options (Sprint / Build / Partner) with clear deliverables and pricing.
Where are you based and do you work remotely?
I’m based in Palisades Park, NJ, and I work remotely with clients in the US and abroad. For onsite needs, short travel is possible with advance notice.
Are you available for consultations or audits?
Yes. I offer short consultations and focused audits (performance, experimentation, architecture). You’ll get a prioritized findings list, quick wins, and a roadmap for deeper work if needed.
Timeline
- Built AI SaaS (Next.js, Supabase, Stripe) scaling to 2,000+ users with paid conversions
- Integrated OpenAI Responses API with live search for idea generation and validation workflows
- Architected modular APIs and database schemas enabling CX agents, compliance copilots, and real‑estate analytics