Rafael de Carvalho

Senior backend engineer. I make the scary parts of a system boring: event pipelines, payments and the migrations nobody wants to touch.

Get in touch See the work

Two billion events a month.

Analytics ingestion rewritten from legacy PHP to Node.js and TypeScript, landing in a columnar store. Queries that used to time out now answer in ~250 ms.

Every message, once.

Queues retry, banks resend, networks lie. Idempotent consumers and transactional side effects make each event count exactly one time.

R$10M a month, reconciled.

Direct APIs with Bradesco, Banco do Brasil, Cielo and Omie replaced FTP files. ~15.5k transactions a month now match themselves.

Noise in. One entry out.

A double-entry ledger built from zero: every movement is a debit and a credit that agree. Six years of making systems add up.

Work with me Try the ledger

Three rebuilds at once, one engineer.

At Chaves na Mão I am the only engineer on three simultaneous platform rebuilds, reporting directly to the CTO.

Analytics that stopped timing out

Analytics pipeline rebuild · Chaves na Mão

Every query timed out against ever-growing MySQL shards. I benchmarked Kinesis Firehose, Redis Streams and in-memory buffering, chose Tinybird as the columnar store, and rewrote ingestion end to end. Advertisers now get real-time dashboards that were impossible before.

~2Bevents a month

~250 msaverage query

Node.js, TypeScript, Kinesis, Tinybird, AWS

Average dashboard query, before and after

MySQL shards timeout

Tinybird pipeline ~250 ms

Drawn to scale against a 20 s gateway timeout.

Payments that reconcile themselves

Payments platform rebuild · Chaves na Mão

File and FTP bank exchanges became direct API integrations. Reconciliation now runs automatically across the internal admin, the fiscal system, every bank and the acquirer, on top of a double-entry ledger I designed from zero.

R$10M+reconciled a month

100%automated

Node.js, TypeScript, PIX, Bradesco, Banco do Brasil, Cielo, Omie

One PIX received, as the ledger records it

// every entry balances or the transaction rolls back
await ledger.post({
  idempotencyKey: 'pix:E1847…3f2a',
  lines: [
    { account: '1.1.02 bank:bradesco',    debit:  1240_00 },
    { account: '2.1.04 customer:credit', credit: 1240_00 },
  ],
});

A PHP monolith, strangled safely

PHP 5.6 to NestJS migration · Chaves na Mão

About 175,000 lines of PHP 5.6 moving into a NestJS monorepo with the strangler fig pattern. Architecture, module boundaries, tests and incremental cutover, while paying customers keep using the legacy system every day.

~175klines of PHP

800+commits

NestJS, TypeScript, monorepo, PHP 5.6

At the edge, each route goes to whoever owns it now

// migrated routes answer from NestJS, the rest still reach PHP
const migrated = new Set([
  '/api/listings', '/api/leads', '/api/billing',
]);

app.use((req, res, next) =>
  migrated.has(routeOf(req))
    ? next()
    : legacyProxy(req, res));

Send it twice. Count it once.

Banks resend webhooks. Fire the same payment again and watch the books. Then turn idempotency off and see what a retry costs.

Idempotency keys

Money receivedR$ 0,00

Credit bookedR$ 0,00

Books balanced. Nothing received yet.

POST /webhooks/pix0 requests

Waiting for the bank. Press “Receive a new PIX”.

This demo needs JavaScript. The idea: each webhook carries the bank's end-to-end id; the consumer stores it in the same transaction as the ledger entry, so a resend finds the key and books nothing.

From intern to sole engineer in six years.

I switched careers at 31. Three promotions in my first two years, and another at Chaves na Mão after three months.

Oct 2025 – now

Senior Backend Engineer

Chaves na Mão · remote

Sole engineer on three platform rebuilds, reporting to the CTO
Promoted after three months, employee of the month
Analytics from timeout to ~250 ms at ~2B events a month
Direct bank APIs and automatic reconciliation on R$10M+ a month

Mar 2025 – Oct 2025

Backend Engineer

TODOS Empreendimentos · remote

Distributed systems in Node.js and TypeScript
Left for broader technical ownership at Chaves na Mão

Sep 2020 – Jan 2025

Intern to Specialist

BGC Brasil · remote

Recurring billing gateways moving ~R$18.5M a month for 600k+ subscribers
Payment processor, acquirer and bank integrations
Upwork in parallel: 225 hours, 100% job success, all in English

The stack, by years in production.

Languages & runtime

TypeScript 6 yr
Node.js 6 yr
SQL 6 yr
Python 2 yr

AWS & messaging

AWS 6 yr
Serverless 6 yr
SQS · SNS 5 yr
Kinesis 1 yr

Data

MySQL 6 yr
PostgreSQL 6 yr
MongoDB 6 yr
DynamoDB 6 yr
Tinybird 1 yr

Frameworks & infra

NestJS 2 yr
Docker 6 yr
Terraform 1 yr

My focus is correctness under load: idempotent consumers, transactional side effects, and enough observability to know before the customer does.

Based in Curitiba, Brazil. Fully remote, comfortable with US time zones, and every Upwork contract I have delivered was in English.

5.0Upwork rating

100%job success

225 hcontracted on Upwork

600k+subscribers billed at BGC

Have a system that has to add up?

Open to senior backend roles, remote, anywhere.

Email me