Case Study

Rebuilding a $4M ARR fintech ledger in 14 days.

How OBSADO replaced a legacy Rails monolith with an edge-native architecture, cutting p95 latency from 820ms to 47ms.

  • React 19
  • TanStack Start
  • Postgres
  • Neon
  • Astro
  • Tailwind v4
  • Vercel
Architecture Diagram
End-to-end request path: edge worker → Neon Postgres → typed RPC.

The Problem

The client operated a mission-critical ledger on a Rails 5 monolith. Reads averaged 820ms, deployments took 45 minutes, and the team burned two engineers a month firefighting migrations.

Their board mandated a rebuild in one sprint. Every incumbent vendor quoted six months. We had fourteen days.

The Engineering Solution

We collapsed the stack into a single TanStack Start application deployed on Cloudflare Workers, backed by Neon Postgres with branching for zero-downtime migrations. Server functions replaced the entire REST surface with typed RPC.

Row-level security was ported directly into Postgres, eliminating an authorization service. Reads dropped to 47ms at p95. Deployments now ship in 90 seconds.

The client shipped to production on day 12. We handed over the repo on day 14.

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