Yuichi Sato

@yasaichi

Software Engineer at a Tokyo-based company

Tokyo, JapanJoined October 2022

About

Typescript/Effect enthusiast, Functional Programming pragmatist, Co-author of “Perfect Ruby on Rails“, ex-CTO at a public company.

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Yuichi Sato's blogs

web complexblog.yasaichi.com8 posts

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Recently published

YSYuichi Satoblog.yasaichi.comDec 1, 2025 · 4 min read

Choose Languages for Leverage, Not Loyalty

For most of modern software history, choosing a programming language meant navigating limitations.Ecosystems, tooling quality, runtime guarantees, and team experience forced trade-offs. Language decisions were as much about constraints as they were a...

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YSYuichi Satoblog.yasaichi.comNov 8, 2025 · 3 min read

When You See Abstract Structures, Design Becomes Easier

While developing an e-commerce system, I once designed a model called DeliveryDateConstraint to represent delivery restrictions decided by sellers. At first, it looked simple enough: each product had its own shipping rule.But later I realised that cu...

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YSYuichi Satoblog.yasaichi.comMay 25, 2025 · 1 min read

Presentation (JA): TSKaigi 2025

Deck https://decks.yasaichi.com/20250524/pragmatic-functional-programming-in-typescript Abstract Functional programming concepts such as pure functions, immutability, and monads are increasingly familiar to TypeScript developers, yet many struggle ...

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YSYuichi Satoblog.yasaichi.comApr 28, 2025 · 3 min read

Handling Known and Unknown Unknowns with Testing and Observability

In modern software development, we often face three types of risks: Known knowns: issues we are aware of and understand. Known unknowns: issues we know exist but lack full understanding. Unknown unknowns: issues we neither know exist nor understan...

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YSYuichi Satoblog.yasaichi.comMar 16, 2025 · 2 min read

Improving Primary Key Performance: Alternatives to UUID v4

In many applications, a primary key must be unique and hard to guess. Developers often choose UUID v4 for these benefits. However, there are trade-offs in performance. Pros and Cons of Using UUID v4 as a Primary Key UUID v4 gives global uniqueness an...

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Yuichi Sato

About

Available for

Yuichi Sato's blogs

Recently published

Choose Languages for Leverage, Not Loyalty

When You See Abstract Structures, Design Becomes Easier

Presentation (JA): TSKaigi 2025

Handling Known and Unknown Unknowns with Testing and Observability

Improving Primary Key Performance: Alternatives to UUID v4

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Yuichi Sato

About

Available for

Yuichi Sato's blogs

Recently published

Choose Languages for Leverage, Not Loyalty

When You See Abstract Structures, Design Becomes Easier

Presentation (JA): TSKaigi 2025

Handling Known and Unknown Unknowns with Testing and Observability

Improving Primary Key Performance: Alternatives to UUID v4