High-volume production API
Visa Card Eligibility Service
Real-time eligibility and benefit redemption APIs — .NET Core and Spring Boot microservices at production scale.
.NET CoreSpring BootC#JavaSQL ServerREST
Projects
Selected work
Systems I've built across payments, financial data, and real-time products — with the constraints they solved and the results they shipped.
CRDT sync + durable log
Real-Time Collaborative Editor
Yjs + Monaco over Socket.IO with append-only Postgres log, snapshots, and Clerk-secured relay.
React 19YjsMonacoNode.js+2
Case study
Archived · full stack docs
Mobile Events Social Platform
Expo + Firebase vertical slice for IRL-first social — messaging, events schema discipline, and TestFlight playbooks (archived).
React NativeExpoFirebaseTypeScript+1
Real-time benefit orchestration
Visa Digital Benefits Platform
Benefits orchestration for issuers — real-time activation, tier rules, and banking integrations on Spring Boot.
Spring BootJava 17IBM DB2REST APIs
Visa Click to Pay
Streamlined cardholder checkout — legacy Backbone/jQuery front end with modern React migration paths.
ReactTypeScriptBackbone.jsSpring Boot
30% faster legal review
GenAI Contract Assistant
RAG pipeline for contract redlining — ~30% less manual legal review time in pilot.
PythonLangChainOpenAI APIRAG
Case study
First MERN · 2020–21
First MERN Stack (Memorial Platform)
First production MERN — dual dev servers locally, one origin behind NGINX in prod.
ReactExpressMongoDBAWS+1
Case study
Team capstone · 2022
Team MERN Exam Workflow Capstone
COVID-era clinical UI capstone — displayPatient, exam tables, and serious Redux monorepo practice.
ReactReduxExpressMongoDB+1
Case study
BFF · Public API
Public API Course Dashboard
TypeScript BFF + CRA client — aggregation, rate limits, and API-native filters vs app-tier filtering.
TypeScriptReactExpressJest
Case study
2019 · coursework
MasterPlan (Course Matching)
Tag overlap + prereq checks — explainable matching before frameworks or LLMs.
JavaScriptAlgorithms
Case study
SwiftUI · 2022
macOS Wallpaper Picker
Desktop automation — download full-res photos and apply as macOS wallpaper.
SwiftSwiftUImacOS
Case study
Expo sandboxes
Expo React Native Experiments
Camera, routing, and 3D spikes before the archived Firebase social codebase.
React NativeExpoThree.js
Case study
8 locales · SSR
Perpetual Gems
Angular SSR + Express lead capture — trust-heavy local service UX at perpetual-gems.vercel.app.
AngularTypeScriptExpressTailwind CSS
Case study
Static · token CSS
Astro + Bun Landing Template
Resale-ready marketing shell — one data file for copy, theme toggle, SEO, and e2e on preview.
AstroBunTypeScriptPlaywright
Case study
Web Audio edge cases
Browser Music Visualizer
Wavesurfer + Web Audio in the browser — Goose for scaffolding, manual work on the audio graph.
ReactViteWavesurfer.jsWeb Audio
Case study
Real token streaming
Gemini AI Backend (SSE)
Managed Gemini + SSE streaming, deterministic matching math, and Firebase-backed chat context (experiment A of two).
GeminiFastifyRedisSSE+1
Case study
Quantized 13B · GPU
Self-Hosted 13B LLM Inference
vLLM on a GPU pod — WebSocket spike, batch generate() chunked for UX, and why experiment A’s SSE pattern should have been reused (experiment B).
vLLMFastAPIPythonGPTQ
Gen 3 · Editorial
Personal Website (current)
danielastudillo.io — Next 16, 20+ MDX posts, projects ↔ blog slugs, CWV-first standalone build.
Next.jsTypeScriptTailwind CSSMDX
Gen 2 · Live archive
Personal Website (Next v2 subdomain)
v2.danielastudillo.io — intermediate Next deploy between Gatsby v1 and the current apex site.
Next.jsReactVercel
Gen 1 · Gatsby
Personal Website v1 (Gatsby)
v1.danielastudillo.io — Gatsby + GraphQL time capsule.
Gatsby.jsGraphQLReact
Roguelike Game
ROT.js roguelike with Vite — dungeon combat prototype inspired by Binding of Isaac.
ROT.jsVite.jsJavaScript