itti — Ueno Bank Fintech Systems

The problem

A consumer banking platform and a game economy solve the same underlying problem: model a resource that changes state over time — a loan, a balance, a notification queue — under rules that have to stay fair, predictable, and hard to exploit, at a scale where a single bad edge case becomes a real cost. Fintech doesn’t usually get described that way, but the systems-design skill transfers directly, which is the whole reason this role belongs on a technical game designer’s portfolio rather than being filed away as “the day job.”

What I built

• Engineered microservice architectures using Golang (AWS SQS, event notifications), Java (banking notification systems), and TypeScript (BFFs) to support Ueno Bank’s high-traffic, scalable product ecosystem.
• Led end-to-end frontend development using Flutter for mobile and React/Next.js for web, keeping the experience seamless and responsive across both platforms.
• Spearheaded rapid prototyping and integration of in-house AI tools and workflows to speed up internal production pipelines.

Key decisions

• Treating notification/event systems as the load-bearing part of the architecture — a banking notification (a payment landing, a loan status changing) is exactly the kind of state transition that needs game-economy-grade rigor: it has to fire exactly once, in order, and degrade gracefully if a downstream service is slow. Building this on Golang and AWS SQS rather than a simpler synchronous call is the same trade-off a game makes when it puts replication logic behind an event queue instead of direct state mutation.
• Owning both the Flutter mobile client and the React/Next.js web client rather than treating them as separate teams’ problems meant the underlying business logic (and its edge cases) only had to be reasoned through once, then adapted per platform — not re-derived twice and risk drifting apart.

Outcome

Shipped microservices and cross-platform frontends (Golang/Java/TypeScript backend, Flutter + React/Next.js frontend) into production for Ueno Bank’s consumer banking platform over a one-year engagement, alongside in-house AI tooling that measurably sped up the team’s own production pipeline.