Backend Engineer focused on scalable systems and complex integrations.

+3 years | Java / Spring Boot | AWS | Distributed Architecture

Portfolio

Featured Projects

P/001MonolithE-commerce — Monolithic Backend
2026

E-commerce — Monolithic Backend

Multi-tenant Spring Boot monolith powering register_flow, backoffice, ecommerce-front and field-sales app

Central backend of the B2B ecosystem. REST API powering the onboarding app (register_flow), admin panel (backoffice), B2B web SPA (ecommerce-front) and field-sales app. Layered + DDD, partner-based multi-tenant, with event streaming via Kinesis.

Java 17Spring Boot 3PostgreSQLRedisAWS SQS/SNS/S3Kinesis+3
E-commerce — Monolithic Backend
P/002FrontendE-commerce Front — Multi-Tenant B2B SPA
2026

E-commerce Front — Multi-Tenant B2B SPA

White-label React 18 + Vite for customers and reps

B2B SPA for customers and reps to place orders. Multi-tenant white-label per partner via the `handlerpartner` header. Product browse, cart, checkout, history, delivery dates, payment plans, recommendations and custom sectoring.

TypeScriptReact 18Vite 5Redux ToolkitMaterial-UI v7Ant Design v5+6
E-commerce Front — Multi-Tenant B2B SPA
P/003MobileField Sales Mobile — Offline-First App
2026

Field Sales Mobile — Offline-First App

Cross-platform Flutter sales-force app with Drift (SQLite) and background sync

Cross-platform app (Android, iOS, macOS, Windows, Linux, Web) for sales reps. Customer management, orders, delivery tracking and offline sync. Clean Architecture in 3 layers (domain / infra / presentation) with 2 Dio datasources (ecommerce + integrator).

FlutterDart 3BLoC/CubitDrift (SQLite)workmanagerDio+5
Field Sales Mobile — Offline-First App
P/004AdminBackoffice — Admin Panel with AI Chat
2026

Backoffice — Admin Panel with AI Chat

Next.js 16 + React 19 with Server Components, shadcn/ui and Vercel AI SDK

Modern admin panel replacing the legacy backoffice (CRA + Ant Design). Manages integrations, customers, orders, PIX, banners and reports, with AI chat using AWS Bedrock and OpenRouter via the Vercel AI SDK.

Next.js 16React 19TypeScriptBunTurbopackTailwind v4+11
Backoffice — Admin Panel with AI Chat
P/005MobileRegister Flow — Multi-Step Onboarding
2026

Register Flow — Multi-Step Onboarding

Flutter onboarding app for sellers and customers with doc upload and geocoding

Multi-step onboarding app for the B2B ecosystem. Seller and customer registration with document upload, address with map, contacts and Brazilian validations (CPF/CNPJ, phone). Feature flags switch seller vs buyer flows.

FlutterDart 3.7+BLoC/CubitGoRouter 15GetItDio 5+3
Register Flow — Multi-Step Onboarding
P/006IntegrationIntegration Platform — Client / Middleware / Orchestrator
2026

Integration Platform — Client / Middleware / Orchestrator

Bidirectional bridge between Oracle Winthor and the B2B platform via 3 Java services

Three-service Java set keeping products, customers, prices, stock, orders and notifications flowing between the Oracle Winthor ERP (on-premise at the partner) and the B2B platform. integration-client runs locally, integration-middleware is the central SQS bus, and integration-orchestrator coordinates complex workflows (credit, PIX, order release, reports).

Java 17Java 21Spring Boot 2.7 / 3.2Oracle (Winthor)PostgreSQLAWS SQS+3
Integration Platform — Client / Middleware / Orchestrator
P/007Event-DrivenOffline Integrator — Field Sales API
2026

Offline Integrator — Field Sales API

Spring Boot 3.5 that generates jobs, runs partner-DB queries and feeds the offline app

Dedicated API for the field-sales app. Generates sync jobs, runs queries on the partner SEGS database (read-only) and feeds the app local Drift DB via S3. Hexagonal/clean architecture (core → application → infra), with primary PostgreSQL and secondary SEGS read-only. Dedicated infra in a separate Terraform repo.

Java 17Spring Boot 3.5PostgreSQLRedisAWS S3AWS ECS Fargate+7
Offline Integrator — Field Sales API
P/008IaCInfra Terraform — Ecosystem AWS IaC
2025

Infra Terraform — Ecosystem AWS IaC

Terraform versioning most of the B2B ecommerce across test/hmg/prod/shared

Comprehensive IaC for the ecommerce ecosystem on AWS. Provisions Lambdas + Layers, API Gateway, RDS, S3, VPC/Subnets/SGs, SSM Parameter Store and ECR. Multi-environment (test, hmg, prod, shared) with standardized naming, remote state in S3 and CI/CD on GitHub Actions.

Terraform 1.0+AWS LambdaAWS API GatewayAWS RDSAWS S3AWS VPC+3
Infra Terraform — Ecosystem AWS IaC

What I Solve

Real problems I master and solve with engineering precision

Tech Stack

Technologies I use daily to build robust applications

Java
Java
Spring Boot
Spring Boot
Node.js
Node.js
Flutter
Flutter
Dart
Dart
PostgreSQL
PostgreSQL
Oracle
Oracle
AWS
AWS
Terraform
Terraform
Docker
Docker
GitHub Actions
GitHub Actions
Prometheus
Prometheus
Grafana
Grafana
Datadog
Datadog
Sentry
Sentry
Firebase
Firebase
Java
Java
Spring Boot
Spring Boot
Node.js
Node.js
Flutter
Flutter
Dart
Dart
PostgreSQL
PostgreSQL
Oracle
Oracle
AWS
AWS
Terraform
Terraform
Docker
Docker
GitHub Actions
GitHub Actions
Prometheus
Prometheus
Grafana
Grafana
Datadog
Datadog
Sentry
Sentry
Firebase
Firebase
Java
Java
Spring Boot
Spring Boot
Node.js
Node.js
Flutter
Flutter
Dart
Dart
PostgreSQL
PostgreSQL
Oracle
Oracle
AWS
AWS
Terraform
Terraform
Docker
Docker
GitHub Actions
GitHub Actions
Prometheus
Prometheus
Grafana
Grafana
Datadog
Datadog
Sentry
Sentry
Firebase
Firebase
Java
Java
Spring Boot
Spring Boot
Node.js
Node.js
Flutter
Flutter
Dart
Dart
PostgreSQL
PostgreSQL
Oracle
Oracle
AWS
AWS
Terraform
Terraform
Docker
Docker
GitHub Actions
GitHub Actions
Prometheus
Prometheus
Grafana
Grafana
Datadog
Datadog
Sentry
Sentry
Firebase
Firebase

Backend & APIs

Java 17
Spring Boot
Spring Integration
JPA / Hibernate
REST APIs
Node.js (Lambda)

Mobile & Frontend

Flutter
Dart
BLoC / Cubit
React
Next.js
TypeScript
Vite
Tailwind CSS

Cloud & IaC

AWS ECS
AWS RDS
AWS SQS
AWS S3
AWS Lambda
Terraform
Docker
GitHub Actions

Data & Observability

PostgreSQL
Oracle
Prometheus v3
Grafana
Datadog
Sentry
CloudWatch
João Paulo Oliveira
About

About Me

I'm from Blumenau, SC — Brazil. I joined the tech industry in 2023 with no formal CS background, learning through practice, consistency, and a lot of curiosity.

What drives me is understanding systems end-to-end: not just making things work, but knowing why that decision and not another. That's what makes me actively take part in architecture discussions, not just execute tasks.

Outside of work I'm always studying something I haven't mastered yet — distributed systems, high scalability and software architecture. I believe the best way to grow as an engineer is to expose yourself to problems bigger than the ones you solve today.

How I work

  • I deliver sustainable code, not just code that works
  • I take part in technical decisions with reasoning, not just execution
  • I learn proactively — what I don't know today, I master before I need it
Professional Journey

Work Experience

Aug 2023 - Feb 2024 (7 months)

IT Assistant

Segala's Alimentos

Initial role focused on technical learning and development fundamentals.

Mar 2024 - Jul 2024 (5 months)

Trainee Software Developer

Segala's Alimentos

Actively participated in development tasks, strengthening software engineering fundamentals.

Aug 2024 - Aug 2025 (1 year 1 month)

Junior Software Developer

Segala's Alimentos

Development of more complex features with greater autonomy.

Sep 2025 - Present (7 months)

Mid-Level Software Developer

Segala's Alimentos

I develop robust and scalable solutions, focusing on quality and performance.

2027 - Coming soon

Senior Software Developer

Segala's Alimentos

Next step in career - building complex architectures and technical leadership.

Testimonials

Recommendations

I had the opportunity to work with João for the last 2 years on developing our mobile app, and I can confidently say he was a key piece in building the backend. As a Backend Developer, working with Java and Spring, João directly participated in a large part of implementing our backend structure. Additionally, he contributed significantly to improving query performance and optimizing important parts of the application, always concerned with efficiency and quality. What I like most about working with him is his attitude: he learns fast, understands problems easily, and knows how to discuss solutions maturely, always seeking the best decision for the product. He delivers quickly, but without compromising on best practices and organization, which makes a huge difference day-to-day. I recommend João with total confidence for any team that needs a solid, responsible backend developer committed to results.

Kauan Curbani

Kauan Curbani

Web and Mobile Developer

João is an excellent professional, I had the opportunity to work with him for 2 years and he has always been a dedicated professional, showing from the beginning that he learns easily and is capable of taking on responsibilities. He performed excellently in the projects he participated in. João is and will be a fundamental piece in any team he works with. Therefore, I leave my recommendation for his services.

Fernando Junior

Fernando Junior

Senior Software Engineer

I was lucky to start my career as a developer alongside João Paulo. From the start, his competence and curiosity in problem-solving were always evident. João was a fundamental piece in my professional growth. As a colleague and friend, he never held back from helping — whether explaining something I didn't understand or dedicating hours (sometimes all day) to solve a problem together. What always mattered to him was reaching the best solution. I recommend João with full confidence to any company. Working with him is an experience that elevates everyone around.

Joao Vargas

Joao Vargas

Developer | Full-stack | Java, Spring Boot | React.js, Flutter

I had the pleasure of working with João and can state, with full conviction, that his work is exceptional. I followed his evolution closely, as well as his dedication and constant drive to learn and make things happen. His role was always fundamental, both in decision-making and solution building, thanks to his deep technical knowledge and domain mastery. Working with João is, without a doubt, a valuable opportunity that everyone should have.

Felipe Baer

Felipe Baer

Full-Stack Developer | Web, Mobile and PWA

Backend Lab

Real engineering, not just slides

Four interactive experiences showing how a backend engineer thinks: live metrics, incident simulator, architecture challenges and real technical learnings.

Live
System Monitor

Real metrics from this portfolio: requests, latency and event feed updating every 5 seconds.

P1 Incident
On-Call Simulator

It's 3am. Payments API at 34% error rate. Every decision you make changes the metrics.

18 challenges
Backend Challenges

Architecture, debug, complexity and tradeoffs. Quiz with timer, score and global leaderboard.

6 insights
Today I Learned

Real technical learnings from day-to-day work — things that surprised me or changed how I think about systems.

Open the Backend Lab
Contact

Let's build something great?

Ready to scale your system or start a new project?

© 2026 João Paulo Oliveira. All rights reserved.