Senior Full-Stack Software Engineer

Chris Romero

Senior Full-Stack Engineer - Java (Spring) / Python (FastAPI) / PHP (Laravel) / JavaScript (React.js) *******@*****.*** • 408-***-**** • San Jose, CA • U.S. Citizen • GitHub: available on request SUMMARY

Senior Full-Stack Software Engineer and Applied Mathematician with extensive experience building high-performance, data-driven backend services and scalable applications using Java, Spring/Spring Boot, Hibernate, JSP/Servlet, Python, FastAPI, PHP, Laravel, and React.js. Strong background integrating RESTful APIs, distributed systems, and complex data models. Adept at working across the entire Java stack—Linux, Apache, Maven/Gradle, Tomcat, Jetty, WebLogic, JBoss, MySQL, JSP/Servlet—as well as integrating 3rd-party APIs (PayPal, Stripe, Zoom, YouTube). Experienced in R&D, mathematical simulation, and machine learning. Previous roles include work with NASA Ames, Los Alamos National Lab (DOE clearance), and enterprise engineering for Visa, Lockheed Martin, and large e-commerce platforms. Brings a unique edge through strong mathematical and systems-thinking background, enabling rapid problem-solving and high-quality architecture design.

CORE SKILLS

Languages: Java, Python, PHP, JavaScript, SQL

Frameworks: Spring, Spring Boot, Hibernate, FastAPI, Laravel, CodeIgniter Front-End: React.js, Vue.js, React Hooks, Axios/AJAX, jQuery, HTML5, CSS3, Bootstrap, Foundation Back-End: REST APIs, Microservices, Authentication (JWT), Payment APIs Databases: MySQL, PostgreSQL, MongoDB

Tools: Git, Docker, AWS (learning), Linux, Apache, Maven/Gradle, Tomcat, Jetty, WebLogic, JBoss EDUCATION

M.S. Mechanical Engineering — University of New Mexico (Emphasis: Fluid Dynamics, Numerical Modeling) B.S. Applied Mathematics — New Mexico State University B.S. Mechanical Engineering — New Mexico State University MATHEMATICAL MODELING & SIMULATION

Equation-Based Modeling: ODE/PDE systems, nonlinear dynamics, numerical methods, discretization techniques (FDM/FVM), stability & convergence analysis. Computational Fluid Dynamics: Navier–Stokes modeling, laminar/turbulent flows, compressible & incompressible regimes, gas dynamics, heat transfer, thermodynamics, multiphase & high-speed flows. Quantum Mechanics & PINNs: Schrödinger equation modeling, wavefunction dynamics, operator methods, Physics-Informed Neural Networks (PINNs) for solving PDEs and hybrid physics–ML systems. Statistical & Predictive Modeling: Regression (linear/nonlinear), time-series forecasting (stationarity, autocorrelation, spectral methods), AR/MA/ARIMA models. Machine Learning / AI: Dimensionality reduction, ensemble methods, neural networks, deep learning architectures, supervised & unsupervised modeling. Stochastic & Probabilistic: Monte Carlo methods, stochastic processes, random fields, uncertainty. Optimization Programming: Linear, nonlinear, constrained optimization, operations research. Agent-Based & Complexity Modeling: Emergent behaviors, multi-agent simulations, dynamic interactions. PROFESSIONAL EXPERIENCE

U.S. Tech Lead Full-Stack Software Engineer — TechHive IT Solutions / Generali Group 2024 – 2025 San Diego, CA (remote)

PHP (CodeIgniter), Python (FastAPI) Angular, React.js, jQuery, MS SQL, REST APIs, Azure Key Vault, C#, Payments

● Led a cross-functional engineering team across the U.S. and India, overseeing full-stack development, security modernization initiatives, and API integrations within an enterprise insurance technology environment.

● Architected and implemented an upgrade from legacy authentication mechanisms to OAuth-based authentication integrated with Azure Key Vault, improving credential security, token management, and secrets governance.

● Refactored and adapted existing OAuth libraries to ensure compatibility with the organization’s legacy PHP runtime, maintaining backward compatibility while modernizing authentication infrastructure.

● Upgraded jQuery and associated front-end dependencies to current secure versions, remediating identified vulnerabilities and strengthening application security posture across client-facing systems.

● Developed and executed a cross-functional modernization initiative upgrading the application stack from PHP 5.4 / CodeIgniter 3 to PHP 8 / CodeIgniter 4, refactoring legacy controllers, models, and libraries to align with updated framework architecture, strict typing, improved routing, and enhanced security standards while preserving backward compatibility and production stability.

● Collaborated within a focused modernization team to migrate legacy Angular components to React.js across a multi-tenant codebase serving multiple distinct domains, redesigning UI architecture, refactoring state management patterns, and ensuring functional parity while improving maintainability, performance, and long-term scalability.

● Designed and implemented role-based access control (RBAC) for clients, agents, and administrators, enforcing least-privilege access policies across workflows, reporting modules, and payment operations.

● Collaborated Python and PHP systems, integrating various services into a heterogeneous multi-language backend ecosystem.

● Developed PHP, Java, and C# reference implementations and working integration examples to enable internal teams and external partners to securely consume company RESTful APIs.

● Collaborated with payments infrastructure teams to support secure transaction workflows, API validation, and role-aware financial processing within enterprise systems.

● Optimized MS SQL queries and backend logic to improve reliability, maintainability, and performance in high-availability production environments.

Tech Lead Full-Stack Software Engineer — Von Wolf ITS 2020 – 2024 Los Angeles, CA (remote)

Java (Spring), React.js, Python, MySQL, REST APIs, PayPal, AWS S3

● Led full-cycle development of a secure, mobile-responsive SaaS platform using Laravel REST APIs and React.js SPA, supporting 5,000+ active users while enforcing strong authentication, authorization, and data protection standards.

● Designed and implemented secure API authentication using SPA token authentication, CSRF protection, session hardening, ensuring safe access between React SPA clients and backend services.

● Built a full React.js SPA including routing, global store patterns, Axios abstraction layer, authentication flows, dashboards, and class/session management UI.

● Developed role-based access control (RBAC) for admins, instructors, and end users, enforcing least-privilege permissions across dashboards, reporting tools, and financial workflows.

● Implemented secure payment processing using PayPal REST APIs and IPN, including webhook verification, signature validation, idempotent transaction handling, and protection against replay and tampering attacks.

● Enforced encryption of sensitive data at rest and in transit, leveraging HTTPS/TLS, encrypted attributes, and secure credential management for API keys and payment tokens.

● Built secure subscription and billing workflows, ensuring PCI-adjacent best practices by never storing raw payment details and delegating sensitive card handling to compliant third-party providers.

● Integrated external services (PayPal, Zoom, YouTube, AWS S3, custom Spring services) using secure API keys, scoped permissions, and environment-based secret management.

● Designed and optimized relational data models with a focus on data integrity, privacy, and access control, including secure handling of personally identifiable information (PII).

● Improved API performance and reliability through query optimization, caching strategies, and indexed database access, reducing attack surface from excessive queries and improving system stability under load.

● Developed administrative reporting (HTML, PDF, Excel) with authorization checks and audit-safe access controls to prevent unauthorized exposure of financial and user data. Senior Full-Stack Software Engineer — Brand Theory Group 2018 – 2020 San Francisco, CA (remote)

Python, PHP (Laravel & CodeIgniter), JavaScript, jQuery, MySQL, PayPal/Stripe

● Built and delivered multiple secure e-commerce and membership platforms using Python and PHP, handling authentication, authorization, payments, and user data for production clients.

● Designed backend APIs supporting secure user registration, login, session management, and account lifecycle flows, including password hashing, token handling, and session hardening.

● Implemented role-based access control (RBAC) for administrators, customers, and internal staff to protect sensitive operational and financial data.

● Integrated secure payment gateways (PayPal IPN and Stripe) for checkout and order processing, ensuring webhook verification, transaction validation, and protection against fraudulent requests.

● Ensured secure handling of sensitive customer data, including separation of authentication data from transactional data and enforcement of least-privilege access at the application layer.

● Developed checkout, subscription, and order workflows with defensive server-side validation to prevent tampering, replay attacks, and unauthorized state changes.

● Collaborated with stakeholders to deliver production-ready systems for brands including Fratelli Orsini, Tough Gloves, Pratt & Hart, and Leather Gloves Online, meeting reliability and security expectations for public-facing commerce platforms. Machine Learning Engineer — Makai Ocean Engineering 2015 – 2018 Kailua, HI (remote)

Java, Python, Octave, FFTs, Multivariate Time Series

● Developed multivariate time-series ML models for deep-sea sensor arrays, analyzing trends, stationarity, and noise.

● Conducted time-series decomposition, autocorrelation analysis, and spectral analysis using FFTs.

● Implemented AR, MA, ARMA, regression, and feed-forward neural models for forecasting ocean sensor dynamics.

● Created visualization tools for sensor data in Java and Python to support oceanographers and research teams.

Machine Learning Engineer — Azure Sky Research

2011 – 2015 Oakland, CA (remote)

Java (Spring, Hibernate), JavaScript, jQuery, MySQL, Graph-Node-Edge library

● Designed and built Java, Spring, Hibernate platform using models/controllers, migrations, data modeling, and JavaScript library integration.

● Designed JavaScript modules for registration, authentication, user dashboard features.

● Built a graph-based ML engine using Monte Carlo inference methods, tautologies, axioms, and logical inference.

● Implemented algorithms for logical propagation, node reasoning, complex graph analytics, editing, and analyzing large quantitative graph networks.

Senior Software Engineer — Ziba Group / Visa

2007 – 2010 Foster City, CA

Java, Struts, MySQL, JavaScript, Excel/PDF Reporting

● Refactored and extended financial reporting tools using Java and Struts.

● Designed parameterized input interfaces, new reporting flows, and automated HTML/PDF/Excel exports.

● Built Excel template processing and spreadsheet generation for financial analytics teams. E4 Software Engineer — Lockheed Martin (IS&S)

2004 – 2007 San Jose, CA

Java, JNI, EJB, WebLogic, Oracle

● Built an EJB–JNI interface layer enabling Java systems to call legacy math models in Fortran, Pascal, and C++.

● Developed multithreaded EJB services and performance measurement utilities for JNI interactions.

● Supported cross-platform deployment (Windows/Solaris) with dynamic library loaders and compatibility logic.

Senior Software Engineer — GeoViz (Collaborative Server Engineering) 2001 – 2004 San Jose, CA

Java, Struts, Tomcat, MySQL

● Led development of a 2-tier collaborative mapping platform for command & control environments.

● Implemented Factory and Façade patterns for collaborative session management and event routing.

● Built administrative tools for managing clients, sources, and real-time collaboration state. ADDITIONAL EXPERIENCE (Condensed)

Full details available upon request; these roles are intentionally summarized to keep the resume Java-Python-focused.

SATC - R&D Engineer / Technical Advisor (2023 - Present) NASA Ames — Computer Scientist IV (2001–2003)

Electron Economy — Senior Software Engineer (2000–2001) Bios Group - R&D Engineer (1999-2000)

Los Alamos National Lab — R&D Engineer (1989–1999) G.J. Research — Mechanical Engineer / Modeling Consultant (1996–1997) Mathematics Instructor - Northern New Mexico College (1998-1999)

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