I'm a mechanical engineer teaching myself backend development the way I learned everything else — by building something real. For nearly three years I've studied and built with Java and Spring Boot alongside full-time engineering work, including a modular-monolith inventory and POS backend covering catalog, stock, sales, payments, and refunds end to end, and a full-stack engineering calculator suite live at eng-tools.renzomendoza.com. I don't have a professional software-engineering job yet — what I have is two working systems, a real technical foundation, and the discipline that comes from engineering work where a mistake shows up in the field.
REST APIs and backend systems built with production practices — layered architecture, validation, and test coverage, not just tutorial code.
The other half of full-stack — client-facing tools built with Next.js and deployed for real use, not just local demos.
A modular-monolith backend for a real retail workflow — product catalog with variants and pricing history, inventory stock movements, a full sales lifecycle (open → completed → cancelled), payments and discounts, refund processing with validation rules, and receipt generation.
A live, deployed suite of engineering calculators — electrical (voltage drop, wire sizing, conduit fill, motor FLC), mechanical (pipe sizing, duct sizing, fire pump sizing, pump TDH/power), and fire/life-safety calculations built directly on NFPA 92, 204, and 13 formulas.
Before writing code, I understand the domain — the actual business rules, not just the data model. That habit comes from engineering, where getting the spec wrong shows up in the field.
I build in layers — entities, repositories, services, controllers — with validation and business rules enforced where they belong, not scattered across the codebase.
Service-layer logic gets unit tests with JUnit and Mockito before I call something done, not after something breaks.
Dockerized and deployed to a real VPS, not just running on localhost — so what I hand over actually runs.
Java 21 and Spring Boot on the backend — Spring MVC, Spring Security, JPA/Hibernate, PostgreSQL or MySQL — with Next.js and React on the front end; I've also worked with Angular. Maven, Git, Docker, and Linux/VPS deployment round it out.
Not in a formal employed role yet. My background is nearly three years of full-time mechanical engineering work while building real backend and frontend systems on the side, including a production-deployed inventory and POS backend and a live engineering calculator suite. I'm upfront about that — what I bring is a strong technical foundation and engineering discipline, not a resume full of past dev jobs.
Yes — for scoped backend or full-stack work, I can quote a fixed price. For full-time positions, I'm applying as a backend, full-stack, or software engineer.
Yes — eng-tools.renzomendoza.com is a live suite of engineering calculators I designed and deployed myself, covering electrical, mechanical, and fire protection formulas. The inventory and POS backend is documented on GitHub. Both are real, working systems, not mockups.
Java/Spring Boot, backend, full-stack, or software engineer roles. Open to full-time, contract, or project-based work.
If you're hiring for a backend, full-stack, or software engineer role, I'd like to talk. If you have a scoped project instead, send the details and I'll come back with a plan.