I move ambiguous new ventures, stalled PoCs, and products that become slower with every change toward the evidence and implementation needed for the next decision.
fyber.studio — A cross-store search engine for pre-owned fashionProduct design & development
More developers are not always the answer.
01
The problem is not missing requirements. It is an undefined decision.
Adding detail to a specification does not help when no one has defined what user behavior or business evidence would justify the next investment. The first deliverable should not be a feature list. It should be a testable decision and the evidence required to make it.
02
The PoC succeeds when it runs, not when it answers the business question.
A demo with clean inputs does not show whether people will use it, whether the operation is sustainable, or whether the economics work. If everything must be rebuilt afterward, both the code and much of the learning fail to carry forward.
03
The existing system holds business decisions hostage.
When impact is difficult to predict, tests are missing, and only one person understands the system, even a small change requires a large estimate. What looks like a delivery-speed problem is often an inability to judge and contain the risk of change.
Put decisions and implementation back in the same loop.
I do not simply receive requirements and build them, or offer technical advice and leave. We define what must be learned, implement the smallest reliable way to learn it, and use the result to make the next decision.
01
New ventures, PoCs, and MVPs
Before turning an idea into a specification, we identify the assumption most likely to invalidate it and the evidence needed for the next decision. I build the smallest product that can be tried in a real workflow and carry the result into the next stage of development.
Testable hypotheses and stop-or-invest criteria
A minimum implementation that reaches real users
Measurement, feedback, and the next decision
Data and architecture that can support production
02
Web products and internal systems
Before building the requested screens, I trace the actual inputs, decisions, handoffs, permissions, and exceptions. We remove unnecessary work first, then build the system around the work that remains.
Workflow, permission, and exception design
Interface, API, and data-model implementation
Authentication, payments, and integrations
Migration, operations, and failure handling
03
Improving products that have become difficult to change
Rather than implementing requests in arrival order, I determine whether growth is constrained by user drop-off, operational load, performance, or change risk. Product improvements and the engineering work needed to make the next change safer move together.
Bottleneck analysis from usage and code
Feature, interface, and journey improvements
Performance, reliability, and security work
Tests and incremental redesign
04
Technical decisions backed by implementation
I evaluate architecture, technology choices, estimates, vendor proposals, and existing code in the context of the business constraints. The result is not advice that ends in a meeting: the reasoning is documented, and I implement the critical parts when needed.
Architecture, technology, and estimate review
Roadmap and technical-risk prioritization
Boundaries between vendors, internal teams, and hiring
Design, implementation, and review of critical work
unvalley
Software Engineer
I am a Tokyo-based software engineer. Alongside building products within technology companies, I contribute to open-source software used by development teams around the world.
Yes. Instead of filling in a specification prematurely, we clarify the user, the behavior that needs to change, the business assumption, and the technical uncertainty. Only the minimum scope needed for the next decision is then defined.
Can you work alongside our internal team or development partner?
Yes. I can take responsibility for stalled decisions between business and engineering, difficult architecture, implementation, or review. We define ownership at the start so the role complements the existing team rather than duplicating it.
Can an existing PoC be taken into production?
That depends on its code, data model, authentication, operations, and quality controls. I retain what is sound and replace only the assumptions that do not hold in production. A complete rewrite is not the default.
Do you also build AI features and AI-assisted products?
Yes. I work on AI-enabled workflows, production AI features, AI prototype productionization, and team adoption of coding agents in addition to conventional product development.
Move a stalled product forward.
A 30-minute online conversation about the idea, PoC, existing product, or technical decision that is preventing the work from moving forward.