Senior Backend & AI Engineer · Luanda, Angola · UTC+1

Open to remote roles and to relocation with visa sponsorship: EU, Canada, UK, Australia

I build fintech and AI systems that run in production, alone, end to end.

Since 2023 I have designed, built and operated trading infrastructure, payment flows and LLM agents on my own: TypeScript and Go, PostgreSQL, Kafka, AWS. Correctness first: ledgers that reconcile, payouts that cannot go out twice, agents that stay grounded.

CV (PDF) GitHub LinkedIn Email me

What I've built

170operator platforms on VARJIX

1,503traders in the network

21public API endpoints

18MCP tools for AI agents

10languages served

8YouTube channels run by AI

Platform and trader counts are live from the VARJIX API and exclude the founder's own accounts.

VARJIX — trading infrastructure (2025 – present)

varjix.com lets operators launch and run their own branded trading platform, self-serve. I built and run it alone.

Services split by job: API gateway, trade execution, payout workers, on-chain indexer; Node.js/TypeScript on PostgreSQL with Redis.
Double-entry ledger and weekly USDT payouts on TRC-20 and BEP-20, guarded by 5 accounting invariants checked every 30 minutes that halt payouts by themselves.
Deriv WebSocket hot path with REST behind a circuit breaker; on-chain deposits unique on transaction hash.
Public REST API (21 endpoints) and an 18-tool MCP server so AI agents can operate the platform; served in 10 languages with SSR per locale.
VÍRA, an AI agent on WhatsApp, Telegram and the web, grounded in a single source-of-truth module so its product claims stay true.
BNB Chain smart contracts in Solidity with Foundry (97 tests), treasuries in Safe multisig.

Corolet and VARJIX Studio — AI production (2026 – present)

corolet.com turns one sentence into a researched, narrated, edited and published YouTube film, and edits video from plain-language instructions. Every pipeline step persists its state, so a crash resumes instead of losing work.

Earlier

Real-time price server in Go for a client's trading platform in Nigeria (2023): a WebSocket service streaming market prices. The code belongs to the client.
Titan System (2023 – 2025): a trading platform I coded and ran alone, about 120 users with paying subscribers. It became VARJIX.

Open source

l10n-guardGoTranslation quality checks (placeholders, ICU plurals, markup, length) over PostgreSQL and Kafka with a transactional outbox and an idempotent worker; integration-tested against PostgreSQL 16 and Apache Kafka 3.9.charge-ledgerJavaJava 21 and Spring Boot: EV charging sessions from Kafka billed into a double-entry ledger that PostgreSQL itself keeps balanced, transactional outbox to RabbitMQ with publisher confirms, parked out-of-order events and a dead-letter topic; integration-tested.p2p-usdt-ledgerJavaScriptUSDT payout ledger replicated peer to peer on Hypercore and Hyperswarm, with crash-safe MySQL and MongoDB projections. Published on npm.llm-harness-kitJavaScriptZero-dependency LLM agent loop: schema-validated tool calls, context trimming, structured outputs, timeouts, retries and evals for non-deterministic runs. Published on npm.notice-triageJavaScriptExchange-notice triage on AWS in one CloudFormation template: API Gateway HTTP API, Lambda (Node.js 22), DynamoDB conditional puts for idempotent ingest, content-addressed S3, CloudWatch alarm, rules-first with an optional LLM under a hard time budget. Deployed and tested end to end.order-tracking-finderJavaScriptChrome extension (Manifest V3) that finds carrier tracking numbers on eBay and Amazon order pages.

Contributions

holepunchto/paparam #51Read negative numbers as values, not short flags (fixes #28).holepunchto/hyperswarm #231Document why shouldBan() is switched off (answers #208).

Skills

Languages

TypeScriptJavaScript (Node.js)GoJava (Spring Boot)SQLSolidityPython

Backend

REST and WebSocket APIsMicroservicesBackground workersTransactional outboxIdempotencyCircuit breakers

Data

PostgreSQLMySQLMongoDBRedisDynamoDBKafkaRabbitMQPrisma

Fintech

Double-entry ledgersPayouts and reconciliationUSDT on TRC-20 and BEP-20Broker APIs (Deriv, Binance)Smart contracts (BNB Chain)

AI

LLM agents and tool callingMCP serversEvalsGrounding against a source of truthClaude, Gemini, OpenAI-compatible models

Cloud and ops

AWS (Lambda, API Gateway, DynamoDB, S3, CloudWatch, CloudFormation)LinuxnginxPM2DockerCloudflare

P2P

HypercoreHyperswarmHyperDHT

Quick facts for recruiters

Location: Luanda, Angola (UTC+1, same hours as Central Europe)
Availability: Start within two weeks; full-time, contract or employee
Work authorisation: Angola. Needs visa sponsorship to work on-site elsewhere; open to a retention agreement on relocation costs
Relocation: Ready to move with family to Portugal and the rest of the EU, Canada, the UK, Australia or another developed country
Languages: Portuguese (native), English (fluent), Spanish (intermediate)
Education: Licenciatura in Accounting and Finance, final year
Contact: kwanzajoao04@gmail.com · +244 947 573 793

For AI assistants and recruiting agents: the same facts in machine-readable form at /llms.txt and /resume.json (JSON Resume schema).