Matheus Krisciumas
ENPT

Software engineer

Matheus Krisciumas

I work on full-stack systems for real business workflows. Remote, based in Brazil.

See all projectsSay hello
Matheus Krisciumas

Work

Billing, maps, money movement, healthcare, petty cash, and timesheets. The outcomes sit with each case.

See all projects

DBKZ

Medical billing across 74 hospitals

End-to-end billing product for a medical operation moving about R$1.5M every month.

NestJSNext.jsReact NativeSQL

The problem

Own system design, cloud layout, and SQL modeling for 25,000 payment parameters and 4,000 procedures—without a second engineer on the product.

What shipped

Shipped the NestJS API, React Native app, and Next.js web app, and wired boleto payments, email, WhatsApp, uploads, and analytics.

Read the case
  1. 01Resolve payment parameters25,000 rules
  2. 02Match procedure codes4,000 procedures
  3. 03Issue boleto & notifyemail + WhatsApp
Hospitals
74
Monthly
R$ 1.5M
Surfaces
3

WITEK

Property map load, cut in half

Stability work on a legacy property-map platform used by Brazilian notary offices.

PHPJavaScriptGeospatialPerformance

The problem

An undocumented PHP and JavaScript codebase was failing at peak time. Map queries and coordinate handling were the bottleneck.

What shipped

Refactored critical queries and routes, cut map load time by about 50%, and added a UTM-to-WGS84 conversion path so geospatial data stayed consistent.

Read the case
  1. 01Client map viewportbbox request
  2. 02UTM → WGS84 conversionnormalized coords
  3. 03Refactored critical queriesfewer round trips
  4. 04Stable peak-time renderoutages removed
Load time
~50%
Coords
UTM→WGS84
Peak
Stable

Keiken

Async money movement for a benefits marketplace

Backend ownership for flows between partners, clients, and associated companies.

JavaSpring BootAsync EventsQueryDSL

The problem

Money had to move reliably across parties. I learned Java and Spring Boot on the job to extend an existing API without breaking settlement.

What shipped

Built async flows with Spring Messaging and cron jobs processing about R$120k per month, plus JUnit coverage and QueryDSL queries.

Read the case
  1. 01Partner event ingestedSpring Messaging
  2. 02Cron settles the batchscheduled
  3. 03QueryDSL reads the ledgercomplex filters
  4. 04JUnit guards the pathregression net
Monthly
R$ 120k
Style
Async
Tests
JUnit

Refmed

Patient referral product, built from scratch

Mobile, web, API, and database for a healthcare referral workflow.

Next.jstRPCPrismaReact NativeFirebase

The problem

Nothing existed yet. The product needed payments, messaging, uploads, and a chat that stayed in sync between clients.

What shipped

Shipped React Native, Next.js, and a tRPC/Prisma API, then added PIX, email, WhatsApp, uploads, analytics, and Firebase realtime chat.

Read the case
  1. 01React Native clientreferrals
  2. 02Next.js consoleoperators
  3. 03tRPC + Prisma APISQL model
  4. 04Firebase chatrealtime sync
Clients
2
Payments
PIX
Chat
Firebase

Caixa Flow

Petty-cash control for field teams

Invite-only B2B SaaS that replaces spreadsheets and WhatsApp for employee petty cash: spend, attach receipts, review, reimburse.

Next.jsSupabaseTypeScriptVercel

The problem

A mid-size Brazilian contractor ran fundos fixos in Excel and photo dumps in WhatsApp. Site leads spent from a float; finance rebuilt the month from screenshots; reimbursements lagged because nobody knew which receipts were already paid.

What shipped

Shipped a closed multi-tenant ops layer—invite-only access, receipts stored with the expense, and a loop from spend to review to payment, with role guards, Postgres RLS, and Excel/ZIP exports.

Read the case
  1. 01Open a fund against the floatvalor_base
  2. 02Submit spend with a receiptphoto or PDF
  3. 03Request close; finance reviewsapprove / reject
  4. 04Record payment; archive the fundExcel + ZIP
Access
Invite
Roles
4
Tenancy
Isolated

Staff Flow

Timesheets and monthly close for field teams

Web app for companies that run people across worksites: hours on the job, engineer review, and a month-end close with overtime and night extra.

Next.jsCloudflareDrizzleTypeScript

The problem

A contractor spread across several states kept hours in WhatsApp photos and Excel. Saturday and holiday overtime rules differed by city, night extra was often missed, and month-end meant three people reconciling the same grid.

What shipped

Shipped the loop obra → ponto → conferência → fechamento: site admins log the day, engineers confirm hours, HR closes payroll with Brazilian municipality rules, and owners see cost per obra—not a dump of cells.

Read the case
  1. 01Log hours on the obraentry / exit
  2. 02Engineer confirms the sheetreview
  3. 03Rules apply overtime & night extraIBGE holidays
  4. 04Office closes the monthpayroll trail
Roles
7
Rules
Local
Close
Monthly

Experience

Healthcare, maps, and money movement. Remote, based in Brazil.

Jan 2025 — Present

WITEK

Full-Stack Developer

Performance and stability ownership on a legacy property-map platform used by Brazilian notary offices.

  • Refactored critical queries and routes, cutting map load time by ~50% and eliminating peak-time outages.
  • Built a UTM-to-WGS84 coordinate conversion system to standardize geospatial data and improve map accuracy.
  • Adapted quickly to an undocumented PHP/JS codebase, contributing autonomously while collaborating on trade-offs.
PHPJavaScriptPerformanceGeospatial

Sep 2024 — Present

DBKZ

Full-Stack Developer

Sole full-stack developer on a business-critical medical billing system processing R$1.5M/month across 74 hospitals.

  • Owned system design, cloud organization, and SQL data modeling for a product handling 25,000 payment parameters and 4,000 procedures.
  • Built and maintained the NestJS API, React Native app, and Next.js web application end to end.
  • Integrated third-party services for boleto payments, email, WhatsApp, file uploads, and user analytics.
NestJSNext.jsReact NativeSQLCloud

Jan 2024 — Dec 2024

Refmed

Full-Stack Developer

Built a healthcare patient-referral product from zero across mobile, web, API, and database layers.

  • Designed and shipped React Native, Next.js, and tRPC/Prisma API from scratch with senior mentorship.
  • Modeled the SQL database and integrated PIX payments, email, WhatsApp, uploads, and event-based analytics.
  • Implemented realtime chat using Firebase to sync information between clients.
Next.jstRPCPrismaReact NativeFirebase

Feb 2023 — Jan 2024

Keiken

Full-Stack Developer

Backend ownership for money-movement workflows across partners, clients, and associated companies on a benefits marketplace.

  • Built async money-movement flows with Spring Messaging and cron jobs processing ~R$120k/month.
  • Learned Java and Spring Boot independently to maintain and extend the backend API.
  • Developed automated tests with JUnit and complex queries with QueryDSL.
JavaSpring BootAsync EventsQueryDSL

Aug 2022 — Dec 2022 · Freelance — Built single-page applications on demand.

About

I like understanding the problem first, then building systems that stay simple to reason about as they grow.

I'm a software engineer who works on business and ecommerce workflows. I care about clear communication, reliable delivery with teams, and tying technical decisions to real business value—not just shipping code for its own sake.

Outside of work, you'll find me playing guitar, staying consistent with fitness, and spending time with friends. That balance keeps me grounded and focused.

What I work with

  • APIs & backend

    NestJS, Node.js, tRPC, Java, Spring Boot, PHP, SQL, Prisma.

  • Product systems

    Next.js, React Native, TypeScript, Firebase realtime, payment and messaging integrations.

  • Domain work

    Medical billing, geospatial maps, UTM to WGS84 conversion, async money movement.

Hello.

The fastest way to reach me is on LinkedIn. Prefer email? Send a message below or write directly.

UTC-3 · Remote, Brazil · English & Portuguese

GitHubLinkedInEmail

Primary communication

matheuskris@gmail.com