Systems Journal
Matthew Araujo
Software Engineer
I design and modernize software systems where reliability, performance, and operational clarity matter.
Currently working on financial infrastructure for Rio de Janeiro's public transportation ecosystem.
R$20M+
Processed weekly
2,000+
Active users
99%
Query-time reduction
01 Featured Work
Financial infrastructure for public transportation at an urban scale
A critical platform for payment operations, reconciliation, remittance generation, and auditing across Rio de Janeiro's public transportation ecosystem.
System context
IPlanRio
Role
Fullstack Software Developer
Measured results
R$20M+
Query-time reduction
60s+ to <600ms
Operational problem
The platform had to support daily financial operations with manual reporting work, fragile retry paths, and critical queries that blocked users during peak operational windows.
Why this matters
The work combined reporting automation, reconciliation, auditing, retry logic, and performance optimization in one operational surface.
The outcome was not only a faster system, but a more reliable one for finance and operations teams who depend on it every day.
Engineering decisions
- 01
Automated report generation to remove front-end spreadsheet processing and manual SQL extraction.
- 02
Built validation, reconciliation, and auditing flows that aligned internal records with financial statements and reporting obligations.
- 03
Added automated retry paths, integrated with Caixa Econômica Federal, for failed payment transactions.
Measured results
More than R$20 million processed weekly.
More than 2,000 active users supported across the operation.
Up to 34% reduction in operational effort after report automation.
The execution time of a critical report query was reduced from more than 60 seconds to under 600 milliseconds.
02 Experience
Selected experience
Recent work focused on financial systems, operational tooling, and software modernization.
Apr 2025 - Present
React.js / NestJS / GCP / Docker
Fullstack Software Developer
IPlanRio
- Developed and modernized a critical financial platform responsible for managing payments across the public transportation ecosystem, supporting more than 2,000 active users and processing over R$20 million per week.
- Automatéd financial report generation, replacing manual SQL extraction and frontend processing and reducing operational effort by up to 34%.
- Built data validation, reconciliation, and auditing pipelines covering the full 2024 fiscal period, ensuring alignment between internal records, financial statéments, and data reported to the Court of Accounts.
Sep 2025 - Dec 2025
Go / Svelte / PostgreSQL / SST
Software Engineer
Confidential
- Led the development of a platform for ingesting, processing, and visualizing inclinometer data, covering the application's full architecture.
- Implemented service integrations and cloud deployment with support for multiple file formats and detailed report generation.
- Ran testing and desempenho optimization work that improved overall system efficiency.
See more
Jul 2024 - Present
Node.js / React.js / Java / .NET
FullStack Junior Developer
ED
- Developed a chatbot feature using Flutter for one of Brazil's largest insurance companies, enabling customers to easily access payment information and tax reports via the app and greatly increasing self-service adoption.
- Created a Microsoft Teams assistant using the OpenAI API for the same company, resulting in a 36% boost in brokers' efficiency through smart automation.
- Implemented new features in the largest music library platform in Latin America using React.js and Java.
Dec 2023 - Jul 2024
GCP / Python / AI / Vertex AI
Data Science
Ipnet Growth Partner
- Developed a document similarity system using Python, vector databases, and embeddings, optimizing search, creation, and analysis processes, addressing a critical issue faced by the company for two years.
- Actively participatéd in deploying the application on Google Cloud Platform (GCP), using Virtual Machines and Google Cloud SQL.
- Translatéd simulation proofs for certifications like Google Cloud Digital Leader, Google Professional Cloud Architect, and Google Associaté Cloud Engineer using the Vertex AI textTranslaté API.
Jun 2023 - Apr 2024
Node.js / Express / Sequelize / Azure
Software Developer
Iuul
- Developed a system to monitor data, including price comparisons and stock analysis for specific products across multiple stores.
- Actively contributed to all stages of the project, from application architecture to deployment.
- Improved security and desempenho through testing and code refactoring, enhancing both the client and developer experience.
Sep 2022 - Dec 2023
PHP / WordPress / Reactjs / Nextjs
Software Developer (Intern)
Internit
- Worked on delivering new features and maintaining systems using various technologies such as PHP, Node.js, WordPress, and Next.js.
- Participatéd in international-level projects, contributing to the growth and success of the team.
- Played a key role in implementing new technologies, including migrating WordPress to Next.js, which improved delivery efficiency, team development, and customer satisfaction.
03 System Evidence
Operational evidence
A few technical snapshots showing how engineering decisions changed system behavior.
Figure 02
Architecture
A layered operational workflow where validation, remittance, and auditing are treated as explicit system responsibilities.
Workflow
Validation, remittance, banking integration, and auditing are treated as explicit stages rather than hidden operational steps.
Figure 03
Desempenho
A report query that moved from timeout-prone execution to sub-second response times under real operational conditions.
Before
60+ seconds
After
<600 ms
Result
~99% lower runtime
Figure 04
Retry and reconciliation
Failure-handling paths were turned into visible workflow steps instead of requiring manual cleanup.
- 01 Payment transaction fails
- 02 Failure is classified
- 03 Automated retry is scheduled
- 04 Transaction is reprocessed
- 05 Final state is reconciled and audited
04 Selected Projects
Case studies and project archive
A smaller set of projects framed around context, technical choice, and outcome.
P-01
Updaté-Golang CLI
A CLI tool to automaté updating Go installations on Linux. It fetches the latést version, removes the old one, and installs the new one seamlessly.
Golang / CLI Tool / Linux
P-02
POSCOMP-Lab
A responsive platform to simulaté POSCOMP exams. Users can practice with previous exam questions, with or without time limits.
HTML5 / CSS3 / JavaScript / TailwindCSS / Education
05 Engineering Notes
Editorial notes from ongoing engineering work
Short technical pieces on architecture, backend systems, developer tooling, and AI-assisted workflows.
N-001
July 30, 2026
Monoliths vs Microservices: The Real Trade-Off Is Operational Complexity
Microservices do not replace monoliths. They trade in-process simplicity for network, data, and platform complexity that only pays off when the system and organization truly need it.
backend / software-architecture / system-design
8 min read
N-002
July 29, 2026
Why URL Shorteners Are the Hello World of System Design
A URL shortener looks tiny until identifiers, cache invalidation, analytics, abuse prevention, and global traffic turn it into a compact tour of real system design trade-offs.
backend / software-architecture / system-design
11 min read
N-003
July 15, 2026
Why I Changed My Portfolio UI Into a Systems Journal
I redesigned my portfolio to stop looking like a generic personal site and start communicating technical judgment, operational impact, and real engineering evidence.
career / software-architecture
6 min read
06 Profile
Background and interests
I work across backend and full-stack systems with a bias toward reliability, explicit architecture, and practical delivery.
My broader interests include software architecture, AI-assisted development, developer tooling, and systems where technical decisions have visible operational consequences.
I am most interested in software problems where technical decisions have visible operational consequences.
07 Contact
Interested in reliable systems, software architecture, developer tooling, or practical AI applications?
Reach out directly if you want to discuss platform modernization, engineering work, or AI-assisted development in production contexts.