Alexsandro Freitas

Full-Stack EngineerSolutions Architect

I turn complex business operations into clear, testable systems.

I design backend platforms, cloud integrations, identity flows and event-driven architectures, with an emphasis on observable boundaries, explicit contracts and tests.

Explore selected systems Discuss a hard systems problem
Alexsandro Freitas smiling with his arms crossed
Abstract architecture map A source passes through a contract, model, gate and execution system before producing observable evidence. CONTRACT GATE MODEL SOURCE STORE OBSERVE RECEIPT
Current work · Appfy

Preparing the next body of work.

At Appfy, I’m documenting current product and systems research with the same emphasis on explicit contracts, observable boundaries and testable workflows used throughout this portfolio.

A sanitized public case has not been released yet.

Visit Appfy

System map · abstract

Evidence-led
Evidence-led systems workflow Inputs move through explicit contracts, policy boundaries and execution before evidence and gaps are recorded. INPUTS OUTCOMES API DOC EVENT PRESERVE source CONTRACT boundary GATE decision EXECUTE bounded EVIDENCE GAP RECEIPT

Abstract operating model — a statement of method, not a product architecture or a claim of commercial scale.

01 · Public evidence

Selected systems

Three public engineering cases, edited around architecture, evidence and explicit limits.

System 01 · 2025

Marketplace Service Architecture

A technical marketplace demo built as independent order and invoice services, with asynchronous messaging, documented APIs, containers and automated tests.

  • TypeScript
  • NestJS
  • RabbitMQ
  • MongoDB
  • Docker
View architecture & code

Technical demonstration · no production or endorsement claim

Marketplace service architecture A public API routes orders to a service and asynchronous queue, while invoices are handled by an independent service. PUBLIC API ORDER SERVICE NestJS · REST RABBITMQ INVOICE SERVICE NestJS · REST ORDERS INVOICES OPENAPI
Abstract diagram from public repository evidence Independent services · async boundary · documented APIs
System 02 · Public demo

My Pet Asteroids

A full-stack product demo connecting a Node.js API to a React and GraphQL interface, with 3D visualization and end-to-end tests.

  • React
  • TypeScript
  • GraphQL
  • Three.js
  • Cypress
Explore the full-stack build

Demonstration project · not an AI or scale claim

My Pet Asteroids full-stack map A React interface combines GraphQL data from a Node API with a Three.js visualization and end-to-end testing. REACT UI GRAPHQL typed data NODE API service CYPRESS E2E THREE.JS
Public full-stack surfaces Interface · typed API · 3D view · E2E tests
System 03 · 2022 template

Accredited Portal Backend

A backend template for identity-centric portals, combining documented APIs, authentication, persistence, containers and automated tests.

  • NestJS
  • Keycloak
  • JWT
  • TypeORM
  • OracleDB
  • Jest
Inspect the public template

2022 technical template · UNLICENSED package · no deployment claim

Identity-centric portal backend A portal client obtains identity authorization before reaching documented backend services and persistence. PORTAL IDENTITY NESTJS API OPENAPI DATA
Abstract diagram from public technical evidence Identity boundary · documented API · persistence
Earlier work 2017 · Full-stack foundations Node.js · Express · MongoDB · React · Redux
02 · Method

How I operate

I start by preserving the source, then make the system’s contracts explicit. Automation comes after the boundary is clear. A run is only complete when its evidence, limits and next decision remain visible.

  1. Preserve evidence

    Keep the source and its provenance available for inspection.

  2. Model the system

    Map actors, states, boundaries and the decisions that matter.

  3. Define contracts

    Turn assumptions into explicit inputs, outputs and failure modes.

  4. Automate execution

    Build the loop only after its limits and handoffs are understood.

  5. Expose the gaps

    Validate the boundary, leave a receipt and make the next proof clear.

03 · Trajectory

Experience by eras

2025–now

Current work · Appfy

Product and systems research; public case not yet released.

2023–2025

Enterprise backend & e-procurement

Integrations, cloud services and platform work.

2019–2023

Solutions architecture & full-stack systems

Identity, APIs and event-driven integrations.

Earlier

From interfaces to full-stack products

Front-end foundations growing into complete product systems.

Organizations are shown as publicly listed career history, not as endorsements of this portfolio.

04 · About

Person before persona.

I’m Alexsandro, a software architect based in Madrid. My work has moved from interfaces and full-stack products to enterprise integrations, identity and event-driven architecture. I now focus on making complex systems easier to understand, test and operate.

I care about the part after the prototype: contracts, evidence, failure modes and the interfaces people use to operate a system.

Based in
Madrid, Spain
Working on
Product and systems research at Appfy
Start with the constraint

Have a hard systems problem?

If it involves fragmented operations, integrations, identity, events or operational automation, I’d like to understand the constraint before proposing the system.