Jefferson Valandro
Available for opportunities

Jefferson Valandro

Senior Software Engineer & Tech Lead with 10+ years building scalable systems, microservices architectures, and cloud-native solutions.

Java Spring Boot React Python PostgreSQL Docker CI/CD MLOps

Who I am

Contact Info

Name Jefferson Valandro
Phone +55 (54) 99906-1618
Email jeffev123@gmail.com
Location Brazil
Availability Open to opportunities

Hello! I'm Jefferson

I'm a software engineer with over 10 years of experience, specializing in backend development, system architecture, and API integrations. I've led multidisciplinary teams as a Tech Lead, building scalable systems in Java and delivering projects in the education, logistics, and fintech domains.

Currently working as a Full Stack Developer (PJ) at Montreal, I bring a blend of deep backend expertise — Java, Spring Boot, Hibernate — and modern frontend skills with React. I'm also expanding into MLOps, combining my engineering background with machine learning production pipelines.

I'm passionate about clean architecture, integration patterns, agile methodologies, and sharing knowledge within teams to raise the bar on software quality.

10+
Years of experience
6+
Companies
20+
Projects delivered

Skills & Expertise

Core technologies and methodologies I use to build and ship software.

Languages

Java Python JavaScript SQL

Frameworks & Libraries

Spring Boot Microservices Hibernate / JPA Struts JSP Flask React Material-UI

Data & Infra

PostgreSQL Oracle IBM DB2 Docker RabbitMQ Kafka Maven Gradle GitLab Jenkins CI/CD

Architecture & Integration

System Architecture REST APIs SOAP ERP Integration Monorepo

MLOps & Data Science

MLOps Pipelines Machine Learning Data Engineering ETL iReports

Leadership & Process

Tech Lead Scrum / Agile Code Review Mentoring Best Practices

Work Experience

10+ years delivering software across logistics, education, fintech, and enterprise domains.

Montreal 01/2026 — Present
Full Stack Developer (PJ)
  • Developing backend services for a tax management system used by tens of thousands of Brazilians, built with Java 21, Spring Boot, and Oracle on Azure.
  • Designing and evolving REST APIs and microservices, ensuring reliability and performance for high-volume transactional workloads.
  • Building React frontends and collaborating with cross-functional teams to deliver complete features end-to-end.
Java 21 Spring Boot Hibernate Oracle Azure React
Dexian 07/2025 — 12/2025
Senior Backend Developer
  • Development and architecture of scalable backend systems in Java, with Oracle as the primary database.
  • Integration with infrastructure and information security practices.
  • Definition of best practices, standards, and backend development strategies.
Java 21 Spring Boot Hibernate JPA Microservices Hexagonal Architecture RabbitMQ Oracle GitLab Jenkins CI/CD Maven
Esig Software 11/2024 — 07/2025
Tech Lead
  • Technical leadership of a multidisciplinary team on educational software projects.
  • Architecture and development of scalable systems in Java, ensuring code quality and best practices.
  • Integration with infrastructure and information security across multiple environments.
  • Definition of coding standards, technical guidelines, and development strategies.
Java 7 JSP iReports Hibernate JPA PostgreSQL GitLab Jenkins Struts Gradle
Promob Software Solutions 2021 — 2024
Senior Software Engineer
  • Led ERP modernization initiatives focused on performance, scalability, and system reliability.
  • Implemented new backend features and automated business processes, achieving a 20% gain in operational efficiency.
  • Ensured seamless integration with third-party services and maintained high availability across production environments.
Java 11+ Spring Boot Hibernate JPA RabbitMQ Docker Kubernetes PostgreSQL MySQL MongoDB React Python Jenkins GitLab Maven
Transportes Bertolini Ltda 2021 — 2021
Software Engineer

Operational issue diagnosis, ERP updates, and process improvements for the transport sector.

Java 8 JSP RichFaces iBatis Spring PostgreSQL
Group 2019 — 2021
Software Engineer — ERP & Integrations
  • Integrated REST and SOAP APIs across internal and external systems, improving data flow and reducing operational costs by 10%.
  • Maintained and evolved a legacy ERP built in Visual DataFlex, adding new features and improving system stability.
  • Contributed to backend services in Java, supporting order management and business process automation.
Java 11+ Spring Boot Hibernate JPA RabbitMQ Docker Kubernetes Oracle PostgreSQL MySQL MongoDB Jenkins GitLab Maven
Promob Software Solutions 2013 — 2019
Software Developer
  • Managed order workflows and built integrations between internal ERP modules and external platforms in Java.
  • Evolved critical ERP features with focus on stability, performance, and code maintainability.
  • Participated in REST and SOAP API integration projects, enhancing system connectivity and data consistency.
Java 11+ Spring Boot Hibernate JPA Python JSF Primefaces PostgreSQL Jenkins GitLab JUnit Maven
MTW 2012 — 2013
Junior Software Developer
  • Coordinated data integration project between schools and government, optimizing system communication.
  • Key contributor in introducing the Scrum methodology in the company.
Java 7 JSP RichFaces iBatis Spring PostgreSQL Scrum

Projects

Selected projects showcasing my work in software development, architecture, and data science.

2026

Quantitative swing-trading system for Brazilian and US equities — walk-forward, out-of-sample, Monte Carlo and cost-stress validation, with automated daily screening — plus a 16-year data study on whether running it actually beat investing. 2.3M daily bars, 26 asset classes, and the finding that most of the apparent edge was interest on idle cash.

Python DuckDB pandas NumPy Streamlit GitHub Actions
2023 — Present

Brazilian investment analysis platform for IBXX stocks and FIIs. Monorepo with Flask API, React frontend, data pipeline, and Docker orchestration.

View on GitHub
2024

Automated documentation tool that instruments functions with decorators to capture calls, arguments, return values, and generate live interactive flowcharts.

View on GitHub
2025

Full AI bootstrap for any project — spec-driven workflow, real-time quality auditor, TUI for feature lifecycle management, AI-powered smart commits, and Claude Code hooks. Detects your stack and configures everything with one command.

Claude Code Bash Python TUI AI tooling
2025

CLI tool that points at any codebase and generates a self-contained HTML report with an interactive architecture graph, health scores, anti-pattern detection, dependency cycle detection, and refactoring suggestions — powered by Claude Code.

TypeScript Node.js Claude Code Cytoscape.js
2025

Full-stack web platform for traders: trade journal with P&L, R:R, Sharpe/Sortino and psychology tracking; multi-indicator backtesting engine (up to 15 indicators) with async BullMQ queue; DCA simulator; Volume Profile (POC/VAH/VAL); and market scanner with alerts.

React NestJS Python FastAPI BullMQ PostgreSQL Redis
2025

Production-ready cloud-native task management platform built with FastAPI, PostgreSQL, Redis, Docker, and full Observability + CI/CD stack. Designed to demonstrate scalable backend architecture, background processing, DevOps practices, and SRE fundamentals.

FastAPI PostgreSQL Redis Docker CI/CD
View on GitHub
2025

Native Android app for personal expense tracking with voice and natural language input, offline AI category classification (TF-IDF + LinearSVC in TypeScript), local SQLite storage, and visual monthly reports — no internet required.

React Native Expo SDK 54 TypeScript SQLite FastAPI Whisper
View site
01/2024

Investigates the relationship between food prices and the Brazilian IPCA inflation index, uncovering patterns and identifying notable variations.

View on Kaggle
12/2023

Machine learning model to detect fraudulent credit card transactions using advanced classification techniques.

View on Kaggle
12/2023

Kaggle competition — data exploration, preprocessing, and model training for accurate house price prediction.

View on Kaggle
12/2023

Performance evaluation of various Brazilian investment assets across different time periods.

View on Kaggle

Templates & e-books

Next.js templates with live demos and hands-on e-books that I build and sell under the ValandroUI brand.

Next.js templates Next.js 16 · Tailwind CSS 4 · shadcn/ui · source code

Kairo Admin

from US$ 19

Admin dashboard with 23 screens: data tables, charts, kanban, settings and auth pages. Light and dark themes.

Kairo AI Starter

from US$ 39

SaaS starter with authentication, AI chat with streaming, usage credits and Stripe payments. Runs in demo mode without keys.

Kairo Blocks

from US$ 29

61 landing-page blocks in 14 categories, one file each, with a live preview and code viewer.

Kairo Estate

from US$ 39

Real-estate website with listings on a map, filters kept in the URL, property pages and lead forms.

Kairo Mail

from US$ 29

32 transactional and marketing email templates built with React Email and Tailwind.

Kairo Studio

from US$ 29

Agency and portfolio website with case studies, services with pricing and a project brief form.

Kairo Complete Kit: all 6 templates US$ 119 instead of US$ 184 bought separately.
Get the bundle

Want to try first? Kairo Blocks Lite has 10 free blocks under the MIT license. GitHub Live demo

Free e-books In Portuguese · PDF · free to share, not for sale

E-books on AI & career In Portuguese · PDF · from beginners to Transformers

IA no Fluxo do Dev

Harness, context, spec-driven development, agents and MCP in practice, with a kit that includes an MCP server. 400 pages.

E-books + template code In Portuguese · PDF + full source code of the template it teaches

Visit the ValandroUI store

Articles & Insights

Technical writing on software architecture, MLOps, and data science.

O que a IA não faz por você: como revisei meus templates e e-books antes de vender

I built Next.js templates and e-books with AI. What guarantees quality is the review: the tests, the checks and the mistakes I caught before selling.

Read article
Refactoring with AI: Safe, Systematic Code Improvement Without Breaking What Works

How to use AI to detect code smells, apply Extract Method, Introduce Parameter Object, Replace Conditional with Polymorphism, and Move Method — with the workflow that prevents regressions at every step.

Read article
Design Patterns with AI: How to Detect, Apply, and Avoid Overusing Them

How to prompt AI to identify Factory, Builder, Adapter, Decorator, Strategy, Observer, and Chain of Responsibility opportunities — plus the test that tells you when a pattern adds complexity instead of removing it.

Read article
SOLID with AI: Using AI to Design, Review, and Enforce the Five Principles

How to prompt AI to detect SRP violations, refactor OCP-breaking switches, audit LSP hierarchies, split fat interfaces, and inject dependencies — with working code for each principle.

Read article
Clean Code with AI: How to Keep Your Codebase Readable When AI Writes Half of It

How to prompt AI for clean output, the most common clean code violations AI introduces, and the review protocol that catches them before they land in your codebase.

Read article
MCP for Software Companies: Giving Your AI Assistant a Company Brain

How to build a company MCP server that puts your architecture, coding patterns, and business rules directly into every developer's AI assistant — so the AI knows your system, not just generic best practices.

Read article
Angular Best Practices: Architecture, Performance, and Quality in 2025

Smart/dumb components, OnPush, RxJS pitfalls, Signals, standalone architecture, lazy loading, and testing strategies for production Angular applications.

Read article
React Best Practices: Architecture, Performance, and Quality in 2025

Component composition, hooks pitfalls, state management with React Query and Zustand, memo anti-patterns, code splitting, and testing with React Testing Library.

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Software Architecture Patterns Compared: Monolith, Microservices, Event-Driven, and More

A practical comparison of the most widely used architectures — when each shines, when it fails, and how to choose the right one for your context.

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Code Quality: Common Mistakes Every Team Makes (and How to Detect Them)

The six most destructive anti-patterns, dependency cycles, module health scores, and how to automate architecture quality checks on any codebase.

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Designing Scalable System Architectures

Microservices, DDD Bounded Contexts, CQRS, event-driven communication, and resilience patterns for systems that grow without breaking.

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MLOps: Deploying ML Models in Production

End-to-end MLOps pipeline: experiment tracking with MLflow, model packaging, CI/CD quality gates, canary releases, and feature stores.

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Event-Driven Architecture with Apache Kafka

Topics, partitions, consumer groups, the Outbox Pattern, Event Sourcing, and Schema Registry for building decoupled distributed systems.

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Model Monitoring & Drift Detection in Production

Four-layer monitoring stack for ML: data quality, feature drift (PSI, KS test), performance degradation, and automated retraining triggers.

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Microservices Communication Patterns

REST vs gRPC, API Gateway, Service Mesh, and the Saga pattern for managing distributed transactions without global locks.

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Building Reliable Data Pipelines for ML

Medallion Architecture, idempotency, dbt schema contracts, Airflow orchestration, and late-arriving data strategies for production ML systems.

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Spec-Driven Development: Shipping Features with AI Without Losing Control

How a structured spec lifecycle — Draft, Approve, Implement, Review, Close — turns AI-assisted development from a guessing game into a repeatable, auditable engineering practice.

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AI for Developers: Power, Pitfalls, and How to Use It Right

What AI genuinely accelerates, where hallucinations silently destroy trust, how agents and skills work, and the discipline that prevents over-reliance from eroding your engineering judgment.

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Clean Architecture in Practice

Dependency Rule, concentric layers, and use case isolation: building a TypeScript payment module where the domain core has zero framework dependencies.

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Hexagonal Architecture in Practice

Ports & Adapters with Spring Boot: isolating the domain core, defining ports as interfaces, and writing use cases that are fully testable without infrastructure.

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API Design Best Practices

Resource modeling, HTTP semantics, versioning, consistent error responses, cursor pagination, rate limiting, and contract-first with OpenAPI.

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CI/CD Pipelines for Backend Systems

Pipeline stages, quality gates with SonarQube, Testcontainers, multi-stage Docker builds, GitOps with ArgoCD, and deployment strategies for production.

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Education & Certifications

Postgraduate in Data Science & Analytics
PUCRIO — Rio de Janeiro, Brazil
2024 — 2025 · Concluded
Bachelor's in Systems Analysis & Development
Ftec — Caxias do Sul, Brazil
2009 — 2012 · Academic Honor — Outstanding Student
IBM Data Science Professional Certificate
Coursera — IBM
2023

Let's work together

Open to full-time roles, freelance projects, and technical consulting. Feel free to reach out.