Backend Engineer Laredo, TX

John Guerra

I build backend systems that don't fall over. Java, Spring Boot, distributed architectures — the stuff that runs when millions of people show up at once.

7K+ Concurrent Users Handled
99.9% Uptime Maintained
<50ms Tick Rate Under Load
View Projects Get In Touch
~/john-guerra
$ whoami
john-guerra
$ cat stack.json
{ "languages": ["Java", "Rust", "Python"], "frameworks": ["Spring Boot", "Netty"], "infra": ["Docker", "K8s", "AWS"], "databases": ["PostgreSQL", "MongoDB"] }
$ _
01

Experience

2023 — Present Freelance

Software Engineer

Self-Employed

  • Architected multiplayer game servers from scratch in Java with Netty, deployed across 3 production environments
  • Handled viral launch with 7,000+ concurrent players when a 4M+ subscriber YouTuber announced — diagnosed and resolved bottlenecks within 24 hours
  • Maintained 99.9% uptime through proactive monitoring and JVM tuning, achieving sub-50ms tick rates during peak load
  • Built custom anti-cheat using packet inspection, reducing cheating incidents by 30%
Java Netty OVH JVM Tuning
2020 — 2025 Full-time

Backend Developer

Dragonball Online Global

  • Backend developer on a community revival of a legacy MMO, working with reverse-engineered client code
  • Diagnosed and fixed a 2-year-old stability issue using ProcMon to trace runaway disk I/O that had evaded prior debugging
  • Built Python anti-cheat system from scratch using real-time packet analysis
  • Improved player satisfaction by 40% and grew active users by 15%
  • Established CI/CD pipeline with automated deployment to test environments
Python C++ CI/CD Packet Analysis
02

Projects

01
Featured Project

Stella

AI VTuber & Conversational Navigator

An AI VTuber that co-hosts live Twitch streams with real personality. Custom cognitive architecture with emotional state modeling, inner monologue generation, and relationship tracking across sessions. Increased chat engagement by 60% and doubled concurrent viewership.

Java Spring Boot OpenAI Whisper STT Azure TTS VTube Studio
Visit Stella
02

Fairview

Interview Anti-Cheat Detection

Cross-platform system monitor detecting cheating during technical interviews. Multi-vector detection including process inspection, overlay detection, audio monitoring, and environment fingerprinting.

Rust Windows API Linux Tokio
GitHub
03

Wallet

Zero-Knowledge Password Manager

Inspired by 1Password's architecture. AES-GCM encryption with PBKDF2 key derivation (100k iterations). Passwordless email auth, rate limiting, and security audit logging. Server never sees your passwords.

Java Spring Boot MongoDB Web Crypto API
GitHub
04

SpikeTracker

Valorant Esports Tracker

Real-time esports tracking with WebSockets for live match updates. Spring Boot 3.5, Java 21, JSoup scraping, Prometheus metrics, and a responsive gaming UI.

Java 21 Spring Boot WebSockets Prometheus
GitHub
03

Tech Stack

Languages

Java Rust Python C++ TypeScript SQL

Frameworks

Spring Boot Netty Tokio WebSocket/STOMP

Infrastructure

Docker Kubernetes AWS EC2 PostgreSQL MongoDB Prometheus

Tools & APIs

Git GitHub Actions OpenAI API Azure Cognitive Flyway
04

Let's Build Something

Looking for a backend engineer who can handle scale? I'm open to interesting projects and full-time opportunities.

Email gekkoquestdev@gmail.com GitHub github.com/gekkoquest LinkedIn linkedin.com/in/john-guerra20 Website gekko.quest
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