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
Backend-first · Full-stack
Daniel Astudillo
APIs · Data platforms · Real-time · NYC
Cut a production data path from 21s to ~250ms, took 40% off p95 on a payment API migration, and shipped realtime pipelines at 99.99% uptime. Backend-first — schema design, gRPC, brokers, migrations — with full-stack ownership when that's what ships. I find the wrong layer on the critical path, replace it, and prove the win in production.
01/Selected Work
All projects →
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
02/Writing
All writing →Building a microfrontend platform for data products
Federation type stubs, Auth0 CTE for downscoped tokens, and CI merge blockers for cache headers, CSP, and remote export drift.
May 2026 · 6 min read
Cutting a data API from 21s to ~250ms
Warehouse DML on the request path was the bug. Stage 1 fixed writes; stage 2 fixed reads. Neither stage was query tuning.
May 2026 · 5 min read
An Astro + Bun landing template experiment
I wanted a resale-ready marketing shell: one data file for copy, scroll-driven story sections, theme toggle, lead capture in demo mode, and e2e checks on deploy.
Apr 2026 · 5 min read
03/About
Full story →Backend-first full-stack engineer — I make data paths fast and platforms maintainable.
I'm Daniel, based in New York. I target senior full-stack and backend roles where the work is APIs, data stores, and the systems around them — subscription platforms, payment rails, market data. Most of my experience is there: .NET and Spring Boot services at Visa, a self-directed stretch building realtime and CRDT systems, and data infrastructure plus frontend platform work at S&P Global.
I'm strongest on the backend — schema design, migrations, gRPC, message pipelines — but I routinely own the full path when it matters: Next.js frontends, Auth0, multi-pod caching, microfrontend shells. The pattern is the same: find the bottleneck, pick the right tool, ship with tests and measurable latency.
Case study
21s → <2s → ~250ms
A Data-as-a-Service API was running BigQuery DML on the hot path — 20–30 second queries under load. Storage Write API over gRPC got responses under 2 seconds. Moving the read path to PostgreSQL + EF Core brought hot queries down to roughly 200–300ms. Three architectural decisions, not query tuning.
Read the full write-upOn my own time I ship end-to-end — auth, realtime sync, deploy pipelines — including a collaborative editor with Yjs CRDTs, durable Postgres persistence, and production-style sharing and rate limiting. Full background →