Yohairo Vargas
Yohairo VargasSenior Full-Stack Engineer

You bring the idea. I build the whole thing — and get it shipped.

Here's the short version: you bring the idea, I build the whole thing — web and mobile apps, AI agents, and automations that kill the busywork. Solo, quick, and I stay on it until it's live and actually working.

16+Projects shipped
11+Years of experience
100%Remote & async

What I do

Services

SaaS Engineering

Need the whole product built? I handle it end to end — login, payments, database, and a UI that actually looks good. You get something real, not a prototype.

Automations with n8n

The repetitive stuff eating your team's day — I wire it up in n8n so it just runs. Leads, invoices, and data moving between your tools without anyone lifting a finger.

AI Agents, set up right

Want an AI agent like Hermes actually working in your business? I install it, configure it, and plug it into your tools so it does real work — not just chats back.

Strategic Consultancy

Not sure what to build or which stack to pick? We talk it through. Straight answers on scope, tools, and roadmap so you keep moving forward.

System Architecture

When things need to grow without breaking, I design the foundation — data models, APIs, and infrastructure that hold up as you scale.

Work

Projects

Selected work across full-stack, AI, and automation. Expand any project for the full case study.

Challenge

Mexican medical residents preparing for the ENARM exam had no modern, adaptive study tool — just static question banks. They needed guided clinical reasoning practice at scale, not multiple-choice memorization.

Approach

  • Designed the SaaS from scratch: auth, billing, content pipeline, and an adaptive study engine.
  • Built an LLM-based Socratic tutor that walks users through clinical reasoning instead of handing over answers.
  • Structured 1,000+ clinical cases across 32 specialties with metadata for adaptive sequencing.
  • Used AI-accelerated workflows to ship the full product solo in weeks, not months.

Solution

  • Adaptive case engine surfaces the right case based on user performance.
  • Streaming LLM tutor with guardrails scoped to clinical context.
  • Spaced-repetition progress tracking per specialty.
  • Role-based content admin for authoring and reviewing cases.

Results

1,000+ clinical cases live across 32 specialties
End-to-end SaaS built and shipped solo
LLM tutor that teaches reasoning, not answers

Tech stack

Next.jsTypeScriptPostgreSQLPrismaOpenAI APITailwind CSSStripeVercel

Challenge

Client messages arrived via WhatsApp with no automated triage. Sales leads went cold, meeting scheduling required manual back-and-forth, and support requests got lost. The business needed a conversational agent that understood intent and routed to the correct pipeline automatically.

Approach

  • Phase 1 — Classify intent: lead inquiry, support request, meeting booking, or general.
  • Phase 2 — Match against a knowledge base for context-aware responses.
  • Phase 3 — Route to action: create a ClickUp ticket, schedule a Google Calendar meeting, or trigger human handoff.

Solution

  • Redis-backed conversation memory preserves context across sessions.
  • Rate limiting protects the WhatsApp Business API quota.
  • Modular design — tickets, calendar, and reply pipelines are independently maintainable.

Results

Messages routed to the correct pipeline in seconds
Meeting booking fully automated end-to-end
Lead follow-up no longer requires human intervention

Tech stack

n8nOpenAI APIRedisClickUp APIGoogle Calendar APIWhatsApp Business API

Challenge

Small firms in the DR drowned in unstructured documents with no fast way to find or summarize them. Existing tools were expensive, English-only, and not tuned for local workflows.

Approach

  • Built and own the product end-to-end as a bootstrapped SaaS.
  • Added AI-powered extraction, summarization, and semantic search over uploaded documents.
  • Designed a clean ingestion pipeline with OCR for scanned files.
  • Localized for Spanish-first users and DR business context.

Solution

  • Vector search over embedded document chunks for natural-language retrieval.
  • LLM summaries and metadata extraction on upload.
  • Secure per-tenant storage and access control.
  • Fast, minimal UI focused on find-and-read workflows.

Results

Owned SaaS product serving the DR market
Natural-language search across document libraries
AI summaries cut time-to-answer dramatically

Tech stack

Next.jsTypeScriptOpenAI APIpgvectorPostgreSQLAWS S3Tailwind CSS

Challenge

A tennis academy ran scheduling, memberships, and payments on spreadsheets and WhatsApp. They needed a real mobile product that players and coaches could use daily.

Approach

  • Built a cross-platform mobile app with React Native and Firebase.
  • Modeled academy operations: courts, coaches, class booking, and memberships.
  • Integrated payments for memberships and one-off bookings.
  • Shipped through App Store review to production.

Solution

  • Real-time booking backed by Firestore.
  • Auth and role separation for players, coaches, and admins.
  • In-app payments with receipts and membership state.
  • Push notifications for bookings and reminders.

Results

Live on the App Store
Payments and memberships handled in-app
Replaced spreadsheet + WhatsApp operations

Tech stack

React NativeExpoFirebaseFirestoreStripeTypeScript

Challenge

Independent detailers were juggling Instagram DMs, WhatsApp, and manual invoices to manage bookings — no tool existed that fit their workflow without requiring a developer or months of setup.

Approach

  • Built a multi-tenant architecture where each detailer gets an isolated studio with their own subdomain or custom domain.
  • Designed 8 professional page templates fully customizable — colors, fonts, logos, hero images — with no code.
  • Implemented a complete booking flow: service selection, add-ons, real-time pricing, and calendar availability.
  • Wired Stripe subscription billing with a 14-day free trial and auto email notifications for bookings.

Solution

  • Branded landing page on a custom subdomain, live in under 5 minutes.
  • Online booking with multi-service selection, upsells, and size variants.
  • Stripe subscription billing with trial management and cancellation.
  • Booking dashboard — confirm, complete, or cancel with one click.

Results

500+ clients booked through the platform
30+ detailers onboarded
5-minute average studio setup time

Tech stack

Next.jsTypeScriptPostgreSQLPrismaStripeTailwind CSSVercel

Challenge

TORQD Carbon needed to move their existing site to Shopify without losing their brand identity — and add a 3D product configurator so customers could customize carbon fiber parts in real-time before buying.

Approach

  • Migrated ~40 products with variants (BMW, Audi collections) into a fully structured Shopify catalog.
  • Customized a premium Shopify theme to match the brand's dark, high-performance aesthetic.
  • Integrated the Angle 3D Configurator for 360° views, AR, and real-time customization.
  • Configured Stripe payments, shipping zones, tax rules, and email automation end to end.

Solution

  • Shopify store with full theme customization matching existing branding.
  • 3D configurator embedded on product pages — 360°, AR, real-time options.
  • Complete content and pages migration with SEO basics.
  • Payment, shipping, tax, and email automation fully wired up.

Results

40+ products migrated with variants
3D configurator live on product pages
Full e-commerce automation in place

Tech stack

ShopifyLiquidAngle 3D ConfiguratorStripeJavaScriptCSS

Who I am

About

I'm a Senior Full-Stack Engineer based in the Dominican Republic. I build production web and mobile products, integrate AI features, and design automation pipelines that remove manual work.

I move fast by pairing strong fundamentals with AI-accelerated workflows — shipping complete SaaS products solo, from schema and auth to polished UI. I care about clarity, reliability, and code that other people can maintain.

AI-accelerated delivery

Ship complete products solo, fast, without cutting quality.

End-to-end ownership

Schema, backend, frontend, deploy — the whole stack.

LLM product sense

Real AI features with guardrails, not demos.

Automation mindset

Turn manual workflows into resilient pipelines.

Let's talk

Got a project or an idea?
Let's figure it out together.

Book a free 30-minute discovery call. We'll talk through what you're building, what's blocking you, and whether I'm the right fit — no pitch, just a straight conversation.