AI infrastructure / Security01
Constellation Gate
A multi-tenant security gateway for LLM applications. From first architecture to engineering leadership.
97.4% F1 at 1% false-positive rate Public benchmark · 16 datasets · 12,111 samples OPEN TO ENGINEERING OPPORTUNITIES BRAZIL · UTC−3
HELLO, I’M
Marcus Vinicius Girolneto Sousa
Engineering
Complex Systems.Building What
Matters.
I design and build reliable systems at the intersection of distributed computing, AI infrastructure, and scalable backend engineering.
Distributed systems AI infrastructure & security Backend architecture Engineering leadership
01SELECTED WORK
Engineering with
real consequences.
Systems that protect, coordinate, deliver and account. A closer look at the decisions behind the code.
Distributed systems02
Constellation Protocol
Consensus, state synchronization and recovery in a production distributed protocol. Engineering for the moments when things go wrong.
AI / Fintech / Founder03
Akibo
A personal-finance assistant connecting natural conversation to structured financial operations, with integrity at its core.
SaaS / Fiscal infrastructure04
Arconta
A private SaaS project for Brazilian accounting firms, turning fiscal XML into explainable validation and correction workflows.
Backend infrastructure05
Hookrelay
Durable, signed webhooks with jittered retries, fenced worker leases and a path back from the dead-letter queue.
Security / Cryptography06
Witness
An append-only transparency log with Merkle proofs, signed checkpoints and monitoring that detects conflicting histories.
Financial infrastructure07
Ledger
Double-entry accounting with database-enforced invariants, immutable history and concurrency-safe balances.
02THE ENGINEER BEHIND THE SYSTEMS
Ownership, from the
first decision onward.
years in software engineering.
Still curious. Still hands-on.
Goiânia, Brazil
Remote or relocation · Professional English
Remote or relocation · Professional English
I enjoy solving problems where correctness, performance, and reliability really matter.
My experience spans financial technology, distributed protocols, AI security, and cloud infrastructure. I take ownership of complex systems, from the first architectural decision to production operations.
At Constellation Network, I built an AI security gateway from zero and then led its engineering team. Alongside that, I worked on the core Scala protocol and helped resolve incidents on a live network.
Today, that same approach shapes my independent work: Akibo, Arconta, and open-source infrastructure built around explicit guarantees.
AI infrastructure & security Consensus & state recovery Full-stack technical ownership Correctness under pressure
Read the full resume 03PROFESSIONAL EXPERIENCE
Built over time.
Proven in production.
A path through enterprise software, financial systems, distributed infrastructure and AI security.
2025—26Constellation NetworkSpecialist Software Engineer / Tech LeadSep 2025 — Oct 2026
From a blank page to an AI security gateway.
- Designed and built Constellation Gate from zero, then led its engineering team.
- Owned application architecture, infrastructure and database design; shipped security scanning, caching and verifiable audit records.
- Co-authored the public Gate AI security benchmark. Worked concurrently on consensus, snapshot recovery, synchronization and operator tooling.
2022—25Constellation NetworkSenior Full Stack Software EngineerMay 2022 — Aug 2025
Building across a distributed-ledger ecosystem.
- Built applications, backend services and developer tooling across the ecosystem.
- Maintained a production IoT partner application across mainnet and testnet, including protocol upgrades and reward-distribution logic.
- Built remote deployment tooling with Ansible and Docker, third-party integrations and transaction-pipeline monitoring.
2021—22PagSeguro PagBankSenior Software Development EngineerAug 2021 — Mar 2022
Modernizing systems at a major Brazilian fintech.
- Helped lead a monolith-to-microservices modernization.
- Designed and delivered Node.js/TypeScript and Java/Kotlin services with Micronaut and Jenkins CI/CD.
- Supported engineers through architecture discussions and code reviews.
2021Sistema SaiposFull Stack DeveloperMay 2021 — Aug 2021
Practical engineering for restaurant-management SaaS.
- Delivered features, automated tests and production fixes.
- Optimized PostgreSQL and Oracle queries and worked with AWS services.
2017—21ZG SoluçõesSoftware DeveloperOct 2017 — May 2021
The foundations: enterprise software and production ownership.
- Delivered enterprise product features and customer-reported fixes in Java/Groovy and JavaScript.
- Maintained CI/CD pipelines and automated tests with JUnit and Jest.
Earlier: Technical Support Analyst at SIACON, Apr — Oct 2017. Full history in resume
04ENGINEERING EXPERTISE
Different layers.
One systems mindset.
Tools change. The work is understanding the boundaries, failure modes and guarantees between them.
Backend engineering
APIs, event pipelines and services that stay correct under load.
Applied in Gate, Hookrelay and Ledger.
Distributed systems
Agreement, coordination and recovery across imperfect networks.
Applied in Constellation protocol engineering.
AI infrastructure & security
A reliable boundary between intelligent agents and real actions.
Applied in Gate and Akibo.
Cloud & delivery
Taking ownership from the first deploy to production operations.
Applied across production services and operator tooling.
Data & integrity
Storage models that make the important invariants explicit.
Applied in Ledger, Hookrelay and Akibo.
Product & frontend
Full-stack ownership, with the user at the other end of the system.
Applied in Akibo and distributed-ledger applications.
05ENGINEERING LAB
Don’t just read it.
See how it works.
Small, interactive models of the problems I like to solve. Change a condition. Follow the consequences.
LeaderREADY
01Validator 1WAITING
02Validator 2WAITING
03Validator 3WAITING
04Validator 4WAITING
00 / 03
Ready. One leader and four validators.
Educational simulation · Not the Constellation protocol
Lightweight by design. No paid APIs, accounts or data collection.
rolecall
Permission tests for AI agents. Who can make your agent do what?
ai-agentsauthorizationllm
agent-reliability-lab
Evaluate tool-using incident-response agents with evidence-grounded scoring, fault injection, and reproducible traces.
agentsai-engineeringllm-evaluation
ledger
Double-entry ledger in TypeScript: idempotent postings, database-enforced invariants and concurrency-safe balances. Fastify, PostgreSQL, React.
double-entry-accountingfastifyfintech
hookrelay
Reliable webhook delivery service: retries with backoff, HMAC signatures (Standard Webhooks), idempotency and Postgres SKIP LOCKED workers
backenddistributed-systemsgo
witness
Tamper-evident append-only transparency log: RFC 6962 Merkle inclusion/consistency proofs, Ed25519 signed checkpoints and a split-view monitor
cryptographyed25519go
beacon
High-throughput, privacy-friendly analytics event collector: batching pipeline with backpressure, Postgres COPY sink, UTM and channel attribution
analyticsbackendevent-ingestion
07 WHAT’S NEXT
A GOOD CONVERSATION IS A GOOD START.
Let’s build something
that matters.
I’m interested in challenging engineering opportunities involving distributed systems, AI infrastructure, backend architecture, and technically ambitious products.