Backend systems
Java/Spring Boot, REST APIs, authentication, PostgreSQL, OpenAPI, provider integrations, caching, and CI/CD for production-oriented services.
Alejandro Saez Castells / Valencia, Spain
Senior Backend &Smart ContractEngineer forproduction-gradeWeb3 systems.
I build backend services, smart contracts, blockchain integrations, and workflow systems where roles, permissions, state, deadlines, and reliability matter.
15+ yearsengineering background
4+ yearsbackend, full-stack & Web3 focus
Java / TSSpring Boot and Node.js systems
Solidity / EVMsmart contracts and integrations
portfolio/system-mapProduction mindset
01 / backend systemsAPIs, identity, persistence, integrations
Java, Spring Boot, Node.js, PostgreSQL, Keycloak, OpenAPI, CI/CD.
02 / smart contractsRoles, state machines, deadlines, incentives
Solidity, EVM, Foundry, access control, DeFi primitives, tokenized workflows.
03 / operational softwareInterfaces connected to real processes
Marketplace, aviation, travel, identity, workflow, and developer-tooling systems.
type ProductionSystem = {
boundaries: "explicit";
state: "reliable";
failureModes: "designed";
operations: "observable";
};Core systemsBackend architecture, APIs, smart contracts, and protocol logic
Integration layersIdentity, wallets, providers, databases, blockchain data, and user flows
Operational domainsFintech, RWA, travel, logistics, marketplaces, and workflow automation
What I bring
Engineering depth across backend, contracts, and real operations.
The differentiator is not a longer technology list. It is the ability to model a real process, define reliable boundaries, and carry it through contracts, services, integrations, and product flows.
Smart contracts & Web3
Solidity/EVM, Foundry, wallet flows, contract integrations, DeFi primitives, tokenized workflows, and blockchain-backed state transitions.
Real-world workflow modeling
Operational processes translated into software systems with actors, permissions, deadlines, statuses, KPIs, certificates, and failure paths.
Reliability mindset
Industrial automation discipline applied to backend and smart contract architecture: safety, uptime, maintainability, edge cases, and operational constraints.
Selected work
Case studies in production systems, smart contracts, and Web3 infrastructure.
Selected projects showing backend architecture, smart contract design, blockchain integrations, marketplace workflows, and developer tooling.
Smart contractsFeatured
Solidity / Next.js / TypeScriptSmart contracts + Aviation
Turnaround Checklist dApp
Aviation turnaround operations modeled as on-chain workflows.
A blockchain-based aviation turnaround management dApp where each flight turnaround is represented by a smart contract that tracks ground tasks, deadlines, KPIs, and on-chain certification.
Full-stack productFeatured
Frontend / Backend / KYCFull-stack + Marketplace
AtlasOra Platform
A Web2/Web3 vacation-rental platform focused on trust, search, and smoother guest/host interactions.
A vacation-rental platform combining Web2 product functionality with Web3-oriented features, focused on trusted listings, user verification, search experience, and smoother guest/host interactions.
Backend platformFeatured
Node.js / TypeScript / ExpressBackend + Full-stack
Casper Ecosystem Platform
Unified blockchain, market, and developer data for the Casper ecosystem.
A Web3 platform for the Casper ecosystem combining blockchain data, GitHub project data, and cryptocurrency market data into a unified backend and frontend experience.
Developer tooling
Local infrastructure for faster smart contract iteration.
Fondant extends the portfolio beyond application delivery into repeatable Casper development and testing workflows.
Blockchain toolingInfrastructure
TypeScript / Rust / DockerBlockchain application suite + Blockchain tooling
Fondant
A Ganache-like local testing environment for Casper smart contract workflows.
A blockchain application suite and Ganache-like testing environment for the Casper blockchain, packaging CCTL functionality in a Docker-based UI to improve local development and testing workflows.
Technical focus
Technology grouped by the systems it helps deliver.
My current focus is the intersection of backend systems, smart contracts, and real-world operational workflows.
Smart contracts & protocol logic
Secure smart contract logic, protocol mechanics, incentives, state transitions, and wallet-based workflows.
Backend systems & APIs
REST APIs, service boundaries, authentication, external integrations, and operational backend design.
Full-stack product development
User-facing products that connect interfaces, data, identity, integrations, and blockchain flows.
Data, integrations & infrastructure
Persistence, object storage, CI/CD, local environments, documentation, and third-party provider integration.
Engineering background
Industrial automation shaped how I build software.
My industrial automation background gives me a practical systems mindset: model the process clearly, handle edge cases, keep state reliable, and design for real operational constraints.
Model the real workflow first
Start from actors, constraints, state transitions, and operational risk before choosing the technical shape.
Keep core logic explicit
Make contracts, APIs, and integration boundaries readable enough to review, test, and maintain.
Design for failure at the edges
Treat providers, wallets, networks, identity checks, and external data sources as reliability boundaries.
Use product context to reduce complexity
Build Web3 functionality where it creates traceability, trust, or automation value, not as decoration.
Explore
Read the case studies or review the public engineering profiles.
Architecture, technical decisions, reliability considerations, and project proof are documented throughout the site.