Johnathan K

I worked on the backend data layer for Cylinder Health - a specialized GI care platform that has now helped over 145,000 patients manage digestive conditions through clinician-backed, personalized care plans.

My piece of the stack: the clinical records layer and the EHR ingestion pipeline.

━━━ What "FHIR-compliant" actually means when you build it ━━━

FHIR (Fast Healthcare Interoperability Resources) is the standard that lets healthcare systems talk to each other. In theory it's clean. In practice, every EHR vendor - Epic, Athena, Cerner - sends you data in their own dialect of FHIR, with custom extensions, missing fields, and inconsistent date formats.

So the ingestion pipeline wasn't just "normalize JSON into Postgres." It was:

→ Model the core FHIR resources correctly: Patient, Observation, Condition, CarePlan - each with the right cardinality and relationships

→ Write normalization logic that could handle what real EHRs actually send, not what the spec says they should send

→ Output a PostgreSQL schema queryable by both the application layer (fast, indexed, relational) and the clinical team (human-readable, auditable, filterable by condition/patient/date)

━━━ Why this matters beyond healthcare ━━━

Any platform where multiple data sources feed a single operational layer - fintech aggregators, multi-ERP SaaS, IoT pipelines - hits the same problem: you don't control the upstream data quality, but downstream users expect consistency.

The FHIR normalization pattern translates directly.

Building something in healthtech, or dealing with messy multi-source data ingestion? Happy to talk through the architecture.

If you're a founder with an idea (or a half-built product), I can take it to production.

I'm a full-stack engineer. I help founders go from "we have a Figma" to "we have paying users."

No contractor handoff. No "the frontend dev can't wire Stripe." I own the whole thing - architecture, code, deployment, monitoring.

Here's what I've shipped recently:

→ AI SaaS MVP: zero to first paying customer in 4 weeks (Next.js + Supabase + OpenAI + Stripe)

→ Multi-tenant SaaS: 150+ customer accounts, per-tenant data isolation via Supabase RLS, zero cross-tenant incidents in prod

→ CRM automation: replaced 30 hrs/week of manual data entry with a Python + Twilio webhook pipeline. ROI in month one.

→ RAG internal assistant: cut support response time ~60% for a B2B SaaS team

My stack: Next.js · Supabase · Node.js(Express/Nest.JS) · Python (FastAPI/Django) · Stripe · OpenAI/Anthropic · Vercel · AWS

The founders I work best with usually have one of these problems:

◾ Need an AI SaaS MVP shipped in 4–6 weeks

◾ Want multi-tenant architecture done right from day one

◾ Have "vibe-coded" output from Cursor/Lovable that broke in production

◾ Are stuck on a stalled contractor handoff

If any of that sounds familiar - send me a message. I respond within a few hours and I'm happy to talk through what you're building before any commitment.

8+ years · AI · Fintech · Real estate · B2B SaaS · Healthcare

If you're a founder with an idea (or a half-built product), I can take it to production.

I'm a full-stack engineer. I help founders go from "we have a Figma" to "we have paying users."

No contractor handoff. No "the frontend dev can't wire Stripe." I own the whole thing - architecture, code, deployment, monitoring.

Here's what I've shipped recently:

→ AI SaaS MVP: zero to first paying customer in 4 weeks (Next.js + Supabase + OpenAI + Stripe)

→ Multi-tenant SaaS: 150+ customer accounts, per-tenant data isolation via Supabase RLS, zero cross-tenant incidents in prod

→ CRM automation: replaced 30 hrs/week of manual data entry with a Python + Twilio webhook pipeline. ROI in month one.

→ RAG internal assistant: cut support response time ~60% for a B2B SaaS team

My stack: Next.js · Supabase · Node.js(Express/Nest.JS) · Python (FastAPI/Django) · Stripe · OpenAI/Anthropic · Vercel · AWS

The founders I work best with usually have one of these problems:

◾ Need an AI SaaS MVP shipped in 4–6 weeks

◾ Want multi-tenant architecture done right from day one

◾ Have "vibe-coded" output from Cursor/Lovable that broke in production

◾ Are stuck on a stalled contractor handoff

If any of that sounds familiar - send me a message. I respond within a few hours and I'm happy to talk through what you're building before any commitment.

8+ years · AI · Fintech · Real estate · B2B SaaS · Healthcare