Neftali Hernández

I enjoy building applications that feel great from the inside out: clean, thoughtful, and enjoyable to use. I focus on writing clear, maintainable, and scalable code so projects can grow without losing their essence.

While I have a primary stack, I'm always exploring new tools and technologies. I like to keep moving, try new things, and find fresh ways to improve every project I work on.

You can reach me here:

GitHub Contributions

791in the last year

Less

Full Stack Developer

Jul 2023 - Nov 2025

Keando

Designed and implemented LLM-powered conversational agents (GPT-4, Claude) with RAG over knowledge bases for 10+ clients, reducing average first-response time by 65% and automating the resolution of common queries without human intervention.
Delivered 15+ custom web applications across retail, healthcare, and logistics, meeting agreed deadlines on 95% of deliveries.
Operated production databases with 5,000+ active users and built automation pipelines (ETL/cron) that eliminated the team's recurring manual tasks.
Optimized frontend performance (lazy loading, code splitting, asset optimization), improving LCP by 50%.

Next.jsTypeScriptNode.jsOpenAI APIRAGVector DBMongoDBAPI RESTWebSockets

Full Stack Developer

Nov 2022 - Jul 2023

CargaYa

Built internal tooling for a fintech platform serving the cargo transport sector in Colombia, managing daily operations for 200+ active transporters.
Implemented the digital payment system with support for PSE, Bancolombia, and digital wallets, automating payment reconciliation that was previously manual.
Integrated local payment gateways achieving a 99.5% transaction success rate with zero critical incidents throughout the entire operation period.
Built dashboards with 10+ key operational metrics and AI-generated reports, cutting report generation time from 2 hours down to 5 minutes.

Next.jsTypeScriptNode.jsPostgreSQLExpressStripeREST APIs

Full Stack Developer & Freelance

Feb 2020 - Oct 2022

Terna Labs

Designed and built multiple e-commerce stores from scratch with an average 2.8% conversion rate, including optimized cart, checkout, and product management flows.
Built landing pages for marketing campaigns; in A/B tests, optimized versions lifted visitor-to-lead conversion by up to 35%.
Built a full-featured point-of-sale (POS) system with inventory control that reduced stock discrepancies by 75%.
Integrated Stripe across e-commerce projects, maintaining a 98% transaction success rate.

Next.jsJavaScriptNode.jsStripeMongoDBVercel

Projects

Reentwise

SaaS for landlords that eliminates the friction of rent collection: automated WhatsApp reminders, payment tracking, and centralized financial control.

Meetzeen

Intelligent scheduling platform that connects businesses with their clients, automating appointments and providing full operational visibility.

Experiments

know-cli

Python CLI that indexes a folder of documents and answers natural-language questions while citing its sources: a terminal RAG. Two retrieval modes behind a single interface —lexical (TF-IDF, no API) and semantic (Gemini embeddings)— and it refuses to make things up when the answer isn't in the documents.

PythonRAGTyperGeminiEmbeddingsNumPy

PageKeys

Chrome extension (Manifest V3) to create keyboard shortcuts on any website by pointing at a button with the mouse — no code or CSS selectors required. It generates robust selectors that survive layout changes and supports Gmail-style key sequences (g i, shift+n n).

JavaScriptChrome ExtensionManifest V3chrome.storage API