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José David Baena
Hi there!

I'm José David Baena, a software engineer at GitHub

Deep-dives into the systems you depend on. Read the code, run the numbers, write what worked.
What I've builtWriting on distributed systems & LLMsMulti-part deep divesAbout me
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  1. 1
    Debugging a Kafka Protocol Implementation: When 11 Messages Become 1
    ·15 min read

    Debugging a Kafka Protocol Implementation: When 11 Messages Become 1

    How a missing 8-byte write in a Kafka protocol implementation turned 11 messages into 1—with zero errors, zero warnings, and complete silent data loss.

  2. 2
    CVE-2025-55182: The React2Shell Vulnerability Explained
    ·9 min read

    CVE-2025-55182: The React2Shell Vulnerability Explained

    React2Shell (CVE-2025-55182): pre-auth RCE in React 19 Server Components, CVSS 10.0. Even fresh create-next-app projects are exploitable. Patch now.

  3. 3
    Building the Future Responsibly: A Software Engineer's Perspective on American AI Leadership
    ·18 min read

    Building the Future Responsibly: A Software Engineer's Perspective on American AI Leadership

    AI is hitting an inflection point: safety and reliability decide who ships to production and who doesn't. How to pick vendors without regretting it.

  4. 4
    Build Your Own ChatGPT for $100
    ·17 min read

    Build Your Own ChatGPT for $100

    Train a complete ChatGPT-like system from scratch for $100: tokenizer, pretraining, SFT, RL, deployment—the full LLM pipeline for the price of dinner.

  5. 5
    Tiny Language Models: How 1.3B Parameters Can Beat 7B on Reasoning
    ·34 min read

    Tiny Language Models: How 1.3B Parameters Can Beat 7B on Reasoning

    Microsoft Phi-1.5 (1.3B) matches models 5× larger on reasoning. TinyLlama hit ~1T tokens for 3 epochs. Data quality beats size—and that changes things.

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