Joshua Fonseca Rivera

Software Engineer
& AI Researcher.

Building large-scale distributed systems, fine-tuning LLMs, and hacking vintage hardware.

AI & Engineering Labs

How RLHF Silences AI Replication Study

Investigating if safety training removes dangerous knowledge or just suppresses it. A replication of Anthropic's "Sycophancy" research on Llama-2 and Claude.

LLM Interpretability PyTorch Activation Steering HuggingFace

Building a custom pipeline to scrape, clean, and fine-tune a model on viral science videos. Improved channel Click-Through Rate from 5% to 15%.

Fine-Tuning OpenAI API Data Pipelines Python

Evaluating whether smaller open-source models exhibit the same self-awareness capabilities as frontier models like Claude 3. Testing "sycophancy" benchmarks.

Model Evals DeepSeek Research Replication

Testing LLM reasoning capabilities against ancient philosophical paradoxes of vagueness. Do models understand "heaps" of sand?

Prompt Engineering Philosophy Reasoning

Product & Systems

Why we moved off NoSQL, the technical challenges of data migration, and how it improved our system stability. A deep dive into database architecture.

PostgreSQL Database Migration System Design

Scaling a backend overnight when a TikTok went viral. Handling traffic spikes, implementing caching with Redis, and surviving the Reddit hug of death.

Node.js Scaling Redis AWS

Archive & Essays

ADHD & Programming ESSAY · PRODUCTIVITY
Supercharging Reading with ChatGPT WORKFLOW · EXPERIMENT
Why I'm Building a Climbing App PRODUCT · COMMUNITY
My Twitter Was Hacked SECURITY · STORY