Hi, I'm Lehi Alcantara, a Senior Software Engineer from SLC Metropolitan Area.

Full-Stack Web Application

Tech: Node.js, Express, React, MongoDB, HTML, CSS, Javascript, API Rest Service, WebSocket, Vite.

A collection of full-stack technologies to create/Edit/Delete/Update a personal or shared Quiz Application addressing real user workflows by implementing REST APIs, responsive frontends, and persistent storage. Delivered production-like patterns (auth, validation, testing) so teams can iterate safely.

GitHub | Demo

iOS Mobile Apps Development

Tech: Swift, UIKit/SwiftUI, SwiftData, Foundation, AVFoundation, MapKit, MultiPicker, Xcode.

Built modular iOS apps for interactive learning and task management with offline support. Implemented local persistence and clean architecture to ensure maintainability and smooth UX. Demonstrates professional iOS patterns and app lifecycle handling.

GitHub

iOS Recipe Management App

Tech: Swift,SwiftUI, Foundation, SwiftData, MarkdownUI, Xcode.

Solved the need for personal recipe organization with a searchable, supporting categorization.  Implemented a catalog of recipes allowing user to view/add/remove/edit recipes/categories and responsive UI to support mobile usage with layout responding according to screen space (iPhone & Ipad). Shows MVVM data modeling and user flows.

GitHub

Systems Engineering

Tech: Arduino/ESP8266, Raspberry Pi, MQTT, Python, Highcharts.js, NodeJS, AWS Lambda, Slackbot, MQTT, Shell Scripting.

In a series of seven IoT Systems Engineering projects, I progressively designed and implemented a small-scale IoT system using Raspberry Pi and Arduino-based microcontrollers. Started with a WiFi-controlled LED stoplight server. Then re-implemented this on the Wemos D1 Mini (ESP8266) to optimize hardware efficiency. Ten added a UC-SR04 ultrasonic sensor to measure distance and send GET requests to remotely control the lights through a REST protocol. Then replaced direct control with an event-bus architecture using topic-based messaging for coordination of multiple actuators. Then used relays and created a user interface to control it. Across the projects, I applied state-machine modeling, flowcharts, RESTful communication, and event-driven design—demonstrating embedded systems development, system scalability, and robust IoT architecture design.

Tutorials & Github

Data Engineering ETL Pipelines & Distributed Monitoring Systems

Tech: Python, Shell, Dockerfile,  CockroachDB adapters.

Built ETL pipelines that ingest, clean, validate, and transform raw data into analytics-ready datasets. A modular, Python-first toolkit for monitoring distributed infrastructure. The repo is organized into collectors and scrapers for data ingestion, storage adapters, and small utilities for health checks and security auditing. It includes example checks (e.g., SSH availability and login monitoring), CockroachDB, supporting shell scripts, and a Dockerfile for containerized workflows.

GitHub

IoT & Cyber-Physical Systems Prototype

Tech: Arduino/ESP32, Raspberry Pi, MQTT, Python, Highcharts.js

A “smart scale” prototype where the system integrates physical hardware and software to measure weight and implements a reward system that triggers when users achieve specified goals (like hitting their target weight). Built an end-to-end IoT prototype connecting sensors, edge devices, and cloud dashboards; included MQTT pipelines and alerting. Demonstrated telemetry reliability and remote observability for field devices. Shows embedded-to-cloud engineering.

GitHub | Demo

Dockerized Multi-Service Stack (DevOps)

Tech: Docker, Docker Compose, Oracle Cloud Infrastructure, Node.js, Fastify.js, React,  JavaScript, CSS, Shell scripting, Fastify-CLI, npm scripts for dev/test/prod workflows.

Designed and deployed a full-stack quiz platform using Docker Compose to orchestrate a React-based frontend, Fastify-based API server, and Node.js backend. This project showcases my skills in containerization, microservice architecture, and modern JavaScript development. I streamlined the workflow with dev/hot-reload scripts and made a live demo accessible across multiple service endpoints.

GitHub | Demo

DevOps Automation Scripts & Workflows

Tech: Python, Bash/Shell, Raspberry Pi, Cron, Arduino/ESP8266, Highcharts.js.

Built a modular toolkit combining Python and shell scripts to automate environmental monitoring and control. Includes sensor integration, Raspberry Pi helper tools, scheduled task execution via cron, and real-time data visualization using a hosted temperature chart. Highlights robust instrumentation and system-level automation. Search engines indexing scripts, sending emails for different tasks.

GitHub | Demo

Technical Interview Problem Library

Tech: JavaScript: Core language for solutions and testing.

Curated a robust repository of algorithm and data structure solutions in JavaScript to sharpen coding interview readiness. Organized problem sets by topic—from recursion and sorting to trees, hash tables, and linked lists—paired with in-depth examples and assignments. Demonstrates disciplined skill progression, with clear modular organization and language-agnostic implementation strategies.

GitHub

Task Management Android App

Tech: Java, Android Platform / SDK – leveraging core UI components (ListView, adapters, views) and local file storage mechanisms.

Built a performant, minimalist to-do list app entirely in Java for Android. Features include JSON-based storage for persistent task management, intuitive UI using standard ListView and CheckBox components, and no required user permissions—prioritizing both privacy and efficiency.

GitHub

Web Application Design

Tech: HTML/CSS/JS/ASP.NET

Developed a responsive, minimalistic web application using a classic server-driven approach. Implemented primary content structure in HTML, enhanced styling with CSS, and embedded dynamic logic with ASP.NET for backend functionality. The project represents clean separation of concerns between presentation and logic.

GitHub

Dynamic Web Project Demonstrating Full-Stack Fluency

Tech: HTML/CSS/JS/PHP/Java 

A compact yet robust example of web application skills, this project integrates several programming languages to deliver a dynamic, full-stack experience. Core logic is implemented in PHP, augmented with JavaScript for client-side interactions, and polished with HTML and CSS. Supplementary Java and Perl components reflect versatility in handling scripting tasks or backend utilities.

GitHub

Data Structures Implementations

Tech: Java, JUnit

Clean implementations of lists, trees, heaps, hash, linked list and graphs with unit tests and benchmarks. Shows algorithmic logic understanding and data structure implementations.

GitHub

Discrete Structures & Algorithms

Tech: Java (standard library only: java.util, java.io), Javadoc.

Built a full Datalog pipeline from scratch:

1. a hand-written lexer that tokenizes input,

2. a recursive-descent parser that constructs a rich AST (schemes, facts, rules, queries, domain),

3. an in-memory relational database implementing core relational algebra (selection, projection, rename, join, union), and

4. an interpreter that evaluates rules to a fixpoint and answers queries over derived relations.
   Delivered complete Javadoc and internal docs; no third-party dependencies.

GitHub

Object-Oriented Programming Projects

Tech: C++

Built a structured C++ codebase with three tracks—Projects, Labs, and personal Exercises—to master core language and problem-solving skills. Projects consolidate concepts into small console applications with file I/O and class design; Labs provide focused drills on loops, arrays/strings, functions, pointers, and basic STL; and My Own Exercises capture self-driven practice and refactoring. Primary tech is C++ (STL) with some HTML for notes/demos.

GitHub

Programming Foundations Projects

Tech: C++

Built a comprehensive C++ practice repo split into focused Labs and larger Dev exercises. Labs drill one concept at a time—console I/O, control flow, functions, arrays/strings, pointers/references, basic classes, and STL—while Dev tasks combine multiple ideas into small, maintainable programs with headers/implementations, simple data models, and file I/O. The work emphasizes clean code, iterative improvement, and confidence with the C++ standard library.

GitHub

Wireless & Embedded Systems – Bluetooth Audio Streaming with Control

Tech: ESP32 Firmware — C++ (Arduino framework) for embedded microcontroller code.

• Host Side Script — Python 3 with bluetooth (via PyBluez) for Bluetooth communication. Standard libraries for file I/O and .wav handling — including the wave module.

• Platform — ESP32 hardware (embedded device), paired with a Windows host environment for the Python client.

Engineered an end-to-end audio streaming prototype using an ESP32 and Python. Created embedded firmware (Arduino C++) running on an ESP32 to receive Bluetooth control commands (p, n, q) and orchestrate audio playback. Built a Python 3 client using PyBluez to connect over Bluetooth, stream .wav files from a folder, and send real-time controls. Complemented the system with design documentation, hardware schematics, and working media files for clear demonstration and reproducibility.

GitHub

Web & Social Media Analytics Dashboard - Twitter Streaming & Data Archival Toolkit

Tech: Python — API streaming, data ingestion, MongoDB interaction

• Jupyter Notebooks — data exploration and visualization

• MongoDB — NoSQL storage backend

• Shell (bash) — data extraction and scripting

• Dependencies managed via requirements.txt

Developed a modular Python- and notebook-based system to stream data (e.g., from Twitter), authenticate through auth.py, ingest live data with streaming scripts (stream.py and variants), store results in MongoDB (mongo_db.py), and extract stored data using shell utilities (extractMongoData.sh). The repository pairs clean Jupyter-powered analytics with a flexible, repeatable pipeline.

GitHub | Demo