Product Growth
Lifecycle and conversion work that connects user needs, pricing, onboarding, and post-launch measurement.
Senior Fintech Engineer
Hello, my name is
Yudai Yaguchi
Product-minded Fintech Engineer
I build and operate fintech systems at the intersection of payments, risk/compliance, product growth, and operations tooling. My work turns ambiguous customer and internal workflows into reliable, monitored systems that keep improving after launch.
6+ yrspayments, risk, and product systems
Risk + ComplianceKYC, OFAC, disputes, and monitoring
Product + Opscustomer UX and internal tools
Atlas impact
Fintech work across product, risk, money movement, and operations.
The common thread is owning ambiguous fintech problems end-to-end: define the customer or operations pain, ship the system, monitor the rollout, and keep improving the numbers after launch.
- GrowthProduct initiatives across onboarding, conversion, retention, and lifecycle communication
- PlatformsInternal tools and workflows that help operations teams move with better visibility
- Core flowsWork spanning product UX, risk controls, money movement, support, and analytics
Risk and Reliability
Regulated workflows, monitoring, review tools, and operational controls for sensitive fintech surfaces.
Money Movement
Payment and transaction experiences designed with backend reliability, observability, and supportability in mind.
Operations Platforms
Internal workflows, support tooling, dashboards, and automations that make teams faster and safer.
Sensitive implementation details and private metrics are summarized at a high level here; the focus is scope, ownership, and engineering judgment.
Experience
Senior Software Engineer
Atlas
2025 - Present
1 yr 8 mos
Atlas
Lead engineer on the Infrastructure team, serving as directly responsible individual across parallel workstreams spanning payments, customer-support architecture, and internal platform and API engineering. Designed and built Atlas HQ — a Next.js internal operations platform replacing Retool — including authentication, role-based access control, and migration of all user, risk, dispute, and activity tooling, with rollout to 100% of the support and operations org. Architected the company's end-to-end customer-support system on Intercom with team-based routing, retention and escalation logic, cancel-flow integration, and an LLM library for understanding customer conversations. Owned integration of new payment rails — debit-card instant deposits and a cash deposit network — covering ACH file generation, reconciliation, chargebacks, 3DS, fraud controls, and partial-authorization deposits.
Technologies:TypeScriptNext.jsReactNode.jsFirebaseLLMIntercomPayments
Software Engineer
Atlas
2023 - 2025
2 yrs 0 mos
Atlas
Built and shipped core consumer-facing features in Flutter and TypeScript on Firebase — new-user onboarding, retention, and Plaid bank-connection flows — later transitioning ownership to dedicated teams after moving to Infrastructure. Drove growth of the paid Annual Plan subscription from initial launch into a core revenue stream through pricing UI experiments, new upsell entry points, and funnel analysis. Led the Spanish-language initiative end-to-end — localization quality, KYC decline-rate reduction, ITIN support, and Spanish-market campaigns — improving conversion and approval rates for Spanish-speaking customers. Delivered KYC and OFAC compliance infrastructure including OFAC monitoring, a risk-engine migration, eCBSV/CIP integration, and dispute and Metro 2 tooling, alongside reliability work including an activity-tracking framework, monitoring dashboards, and on-call processes.
Technologies:FlutterTypeScriptFirebaseKYCOFACPlaid
Software Engineer
PayPal
Jun 2020 - Dec 2023
3 yrs 6 mos
PayPal
Built and operated large-scale payment infrastructure handling millions of requests daily using Java and the Spring framework. Designed and implemented payment failure-recovery components spanning HTTP clients, ActiveMQ messaging, batch jobs, caching, and Oracle databases, with Vue-based internal UIs.
Technologies:JavaSpringOracleActiveMQVueBatch Processing
Full Stack Engineer
University of Wisconsin-Madison
Apr 2019 - May 2020
1 yr 1 mo
University of Wisconsin-Madison
Built a full-featured web client for a tutor scheduling system that allowed students to book sessions and administrators to audit schedules and activity. Implemented the UI with React and JavaScript and integrated it with a PHP backend.
Technologies:PHPJavaScriptReact
Front-End Engineer Intern
So-net Media Networks Corp
May 2019 - Aug 2019
3 mos
So-net Media Networks Corp
Built a React, Redux, and TypeScript web client for analyzing online advertising performance. Also supported data science research aimed at improving ad selection model accuracy.
Technologies:TypeScriptReact
Undergraduate Machine Learning Researcher
UW-Madison Department of Materials Science and Engineering
Jan 2019 - May 2019
4 mos
UW-Madison Department of Materials Science and Engineering
Applied YOLOv3 to TEM alloy video frames to detect, count, and track material defects. Built an analysis workflow that measured defect generation and annealing, achieving 0.95 F1 with low-latency detection.
Technologies:Python
Education
- 2023-2025
M.S. in Computer Science
Westcliff University
- 2017-2020
B.S. in Computer Science
University of Wisconsin-Madison
- 2016-2017
B.S. in Computer Science
University of Wisconsin-Superior
- 2013-2016
High School Degree
Waseda high school (Japan)
Published Writing
Organization-published engineering articles on fintech systems, internal platforms, and product reliability.
Why Financial Products Need Explainable States (opens in a new tab)
Why modeling a financial product's status as explicit, explainable states improves reliability, support, and user trust.
Building Fast and Secure Support in Credit-Building Applications (opens in a new tab)
How short-lived, support-scoped session tokens help WebView support surfaces stay fast, secure, and recoverable without exposing a mobile app's primary credential.
Fintech Internal Tools Are Risk Systems: How to Build Them Securely (opens in a new tab)
Explains how fintech internal tools should be treated as risk systems, with action-level permissions, approval workflows, audit trails, request IDs, and idempotent execution for sensitive operations.
Latest Blog
View all postsNotes on engineering, lessons learned, and ideas explored in public.
Making a browser shogi AI stronger — 99 experiments, 3 wins, everything measured
The shogi AI on my blog was weak. Weak enough that I — an amateur 2 dan — beat it comfortably, and weak enough that it lost every single game to climbing silver
Inside Personal Memory — MCP, OAuth, PostgreSQL, and pgvector for Cross-AI Long-Term Memory (Part 2)
Inside Personal Memory — MCP, OAuth, PostgreSQL, and pgvector for Cross AI Long Term Memory (Part 2) Part 1: I stopped re explaining myself to every AI explai
Stopped Re-Explaining Myself to Every AI — Shared Memory for ChatGPT, Claude, and Codex (Part 1)
Every new chat started the same way: I would explain my job, my goals, what had been bothering me lately, and everything I had already tried. I built Personal M
Useful Tools
Production-ready utilities built to solve real-world day-to-day problems.
SettliSettlement Tool
Smart group payment settlement. Automatically finds the optimal transfer plan for complex bill splits.
Optimized SettlementWeighted SplitQR Share
KaimonoShopping List
Smart shopping lists with budgets, categories, sharing, and recurring item reminders.
Budget TrackingRecurring ItemsQR Share
KuizuQuiz Tool
Multiplayer quiz platform with 400+ questions, daily challenges, custom quizzes, and live scoreboards.
Multiplayer RoomsDaily ChallengesCustom Quizzes
MD PreviewMarkdown Viewer
Drag & drop or paste markdown files for instant full-screen preview with GitHub Flavored Markdown support.
Drag & DropClipboard PasteGFM Support
Railway PlannerFictional Rail Tool
Plan fictional railways from national trunk lines down to zoomed station layouts for all 47 prefectures.
All prefecturesService patternsCost simulation
TodoAI Task Manager
Extract tasks from screenshots or text with AI. Manage your todo list with smart input.
Screenshot to tasksText extractionAI-powered
スコアトラッカーScore Tracker
麻雀の素点、ゴルフ、ボドゲ会など — 日付ごとの最終点を記録して累計を追跡。コードで友達と共有できます。
日次スコア記録累計の自動集計コード共有
Coming Soon...
More practical tools are on the way.
Selected Projects
Personal, community, and engineering builds with context on the problem, technical choices, and outcome.
- All
- Web App
- Mobile
- AI/ML
- Console
Community Leadership
AI community leadership in the Bay Area.
Founder & Organizer — JTPA-supported Bay Area AI Study Group
Beyond my fintech work, I founded and lead the Bay Area AI Study Group, a JTPA-supported AI community and self-built platform where Bay Area engineers share projects, articles, and lessons learned.
- MonthlyIn-person AI meetups in the Bay Area, organized and hosted end-to-end.
- Self-builtCommunity platform built with Next.js and Firebase for sharing projects and Q&A.
- JTPALed as a JTPA-supported community for Japanese-speaking engineers in the Bay Area.
Organizer & Host
Plan and run the monthly meetup end-to-end: agenda, speakers, venue, and check-in.
Platform Builder
Designed and built bayarea-ai.com from scratch with Next.js and Firebase.
Curating Member Work
Review and showcase member projects, articles, and tips submitted to the community hub.
Japan–US Bridge
Lead a Japanese-speaking engineer community around AI in partnership with JTPA.
Visit the communityRead the platform case studyView my community profileRead the community write-up
The community runs in Japanese for Bay Area engineers; the platform and event information are also available in English.
Study Lab
Articles and interactive CS labs for learning by reading, running, and checking understanding.
Interactive Games
Playable experiments focused on UX, performance, and game logic design.
Senior Fintech Engineer
Yudai Yaguchi
Biography
Hi, I'm Yudai — a senior software engineer based in San Francisco with 6+ years building production fintech systems across payments, risk, compliance, growth, and operations. At Atlas and PayPal, I have owned payment integrations, KYC/OFAC and dispute workflows, support and risk tooling, monitoring, and customer-facing activation and retention experiences. I am strongest when the problem is cross-functional: turn unclear business goals into a shippable system, coordinate rollout details, instrument the results, and keep improving the customer and operations experience. Outside of work, I lead an AI meetup community for engineers and keep exploring how machine learning fits into everyday products. I'm pursuing an MS in Computer Science at Westcliff University while looking for the next role that blends deep engineering with product ownership.
- 28 years
- San Francisco
- uwyudai@gmail.com
- English, Japanese