IGARASHI DEV
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Senior Software Engineer //

Engineering systems. Creating experiences.

I'm Lucas Igarashi, a Senior Software Engineer in São Paulo building payment, mobile and backend products at Caju used by millions of people, from architecture decisions on an internal AI platform to APIs that run at scale.

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System status · Online · São Paulo
01

About

Technical complexity turned into simple products that are fast and reliable.

Senior Software Engineer building payment and mobile products at Caju. I lead the architectural decisions for an internal AI orchestration platform serving 6 teams and rolled out AI-assisted code review across 4 repositories used by 50 engineers. On the backend, I build services and REST/GraphQL APIs that serve millions of users.

I've delivered features used by 10,000+ companies and 300,000+ users, cut declined transactions by 30%, raised checkout retention by 20% across 50,000+ monthly transactions and improved mobile performance by 30%. I implemented 40+ screens and led planning for 3 critical app flows: bill payments, statements and notifications.

02

Selected work

Independent projects · 2026

P/01 — B2B healthcare marketplace

DentistFinder

Started by connecting dental clinics with dentists by the hour and is now evolving into a marketplace for healthcare professionals in general, from search to confirmed appointment.

Role
Product, design and full-stack engineering
Platform
Responsive web · native app in progress
Status
In development, evolving
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Scope

The marketplace connects both sides of hiring healthcare professionals, starting with dentistry in São Paulo. Clinics search by specialty, equipment, region, rate and open hours, then send a proposal with a server-calculated summary. The professional accepts or declines. Acceptance books the slot, removes it from the public calendar and expires conflicting proposals. After the appointment, both sides confirm it happened or open a dispute.

The foundation proven with dentists (profiles, scheduling, proposals, completion and reviews) is being generalized to other healthcare fields. Medical records, patients and service payments are out of scope by product decision: the focus is hiring between professionals.

What I built

  • Scheduling with recurrence, blocks and DST handling (Temporal/IANA); GiST exclusion prevents overlaps
  • Search with 19 combinable, accent-insensitive filters and continuous availability coverage
  • Idempotent proposals with immutable snapshots, database-clock expiry and a full lifecycle
  • Two-sided completion, disputes, anti-retaliation review publishing and moderation
  • Private storage (R2) with magic-number validation and EXIF stripping
  • Plans and entitlements, admin panel with TOTP MFA and license verification

By the numbers

API routes
113
Automated tests
169
SQL migrations
10+
  • NestJS
  • Next.js 16
  • React 19
  • PostgreSQL 18
  • Prisma
  • Zod
  • TanStack Query
  • Turborepo
  • Vitest
  • Playwright

Screens05

  • Mobile landing

  • Clinic search

  • Professional's calendar

  • Proposal review

  • Booking confirmed

  • Calendar · desktop

  • Two-sided completion · desktop

P/02 — Platform for tennis clubs

TennisMatch

Where tennis meets: players, clubs and coaches in one ecosystem, on and off the court.

Role
Full-stack engineering · mobile, web and API
Platform
iOS/Android app · club web dashboard
Status
Live
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Scope

Three products on one API. The player app brings together the club feed, creating and finding friendly or ranked matches (with Mapbox addresses), scoring with sets and tie-breaks, result confirmation or dispute, head to head, stats, rankings, tournaments and court bookings.

The manager web dashboard handles members, QR code invites, courts and bookings, tournaments with brackets, rankings, lessons, coaches and posts. The API serves both, with separate staging and production pipelines.

What I built

  • React Native + Expo app with Tamagui, light/dark themes, deep links and push
  • Full match flow: create, accept, report score, confirm and share to the feed
  • Joining clubs via QR code/invite and court bookings with status details
  • Moderation (report and block) and account deletion per App Store guidelines
  • Next.js dashboard with TanStack Table, dnd-kit and tournament brackets
  • CI/CD with GitHub Actions, Fastlane and EAS; NestJS backend on Railway

By the numbers

Connected products
3
App tabs
5
Dashboard areas
10
  • React Native 0.81
  • Expo 54
  • Tamagui
  • Next.js 16
  • shadcn/ui
  • NestJS
  • TypeORM
  • PostgreSQL
  • Mapbox
  • Fastlane

App screens10

  • Home and feed

  • Ranking

  • Tournament

  • Match · dark theme

  • Create match

  • Book a court

  • Pending matches

  • Head to head

  • Stats

  • Tournaments

  • Website · mobile

03

Experience

Caju · 2021 to present
  1. — Present

    Senior Software Engineer Caju

    • Shipped a smart balance feature adopted by 10,000+ companies and 300,000+ users, cutting declined transactions by 30%
    • Led the architectural decisions for an internal AI orchestration platform serving 6 teams and presented it at the company's architecture review
    • Rolled out AI-assisted code review across 4 repositories used by 50 engineers, reducing time to first review by 40%
    • Mapped 50+ untracked routes and set up route-level error monitoring for the mobile app
    • Owned estimation, delivery and risk communication for 5 payments and benefits features with 8 engineers, all shipped on the original estimate
  2. — 07/2026

    Mid-level Software Engineer Caju

    • Helped rewrite the mobile app from React Native to Flutter, improving overall performance by 30%
    • Implemented 40+ screens and led planning for 3 critical flows (bill payments, statements and notifications) while rolling out the new design system across 150+ screens; the project won an iF Design Award
    • Built custom and multi-category benefit balances, used by 2,000 companies within 3 months of launch
    • Handled 15+ production incidents a month and rewrote the team's debugging docs, cutting average resolution time by 35%
    • Refactored 15+ legacy screens, raising test coverage from 30% to 80%
  3. — 07/2024

    Junior Software Engineer Caju

    • Merged 3 checkout flows into one handling 50,000+ monthly transactions, improving checkout retention by 20%
    • Built the frontend for a new product that generated over R$1M in revenue in its first year
  4. — 2022

    Customer Assistant Caju · Customer Success Quero Educação

    Before engineering, customer support. That's where I learned to see the product from the user's side.

Recognition

iF Design Award: Caju app redesign with a new design system across 150+ screens.

View on iF Design
04

Stack & capabilities

  • Frontend

    React, Next.js and TypeScript. Accessible interfaces, design systems and real-world performance.

  • Mobile

    Flutter and React Native/Expo. RN→Flutter migration, app architecture and route-level observability.

  • Backend

    Node.js/NestJS, Kotlin, Scala and Python/FastAPI. Services and REST/GraphQL APIs serving millions of users: payments, idempotency and reliability.

  • Architecture

    Domain modeling, documented decisions and systems that grow without rewrites.

  • Cloud & data

    AWS, Docker, PostgreSQL and CI/CD. From the right database constraints to automated deploys.

  • Applied AI

    LLM APIs, RAG, agent orchestration and AI-assisted code review at scale.

  • Performance & observability

    Route-level monitoring, faster incident resolution and 30% better mobile performance.

Education

Associate Degree in Systems Analysis and Development

FIAP · 2021 — 2023

Certifications

  • Mobile Application Development
  • Web 2.0 Development & Design
  • C# & Object-Oriented Programming
  • Complete React Course
  • Digital Entrepreneurship & IT Management
05

Principles

  1. 01

    Engineered to evolve.

  2. 02

    Complexity, made elegant.

  3. 03

    Beyond the code.

06

Contact

Let's build
something that lasts.