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[Ferrokinetic][Product][Build Log] August 1, 2026

BUILD_LOG_001 // The Idea: Why I Started Building Ferrokinetic

From Spartan Race training to Notion databases: the origin story of Ferrokinetic and managing cognitive load versus physical endurance.

Author: Denis Ciglarič// Read Time: 2 min

The Friction Point: Code vs. Endurance

Architecting enterprise e-commerce systems requires intense, prolonged cognitive focus. Sitting at a desk for 8–10 hours solving complex data synchronization pipelines is the exact opposite of what your body wants when preparing for extreme endurance events.

When I decided to sign up for my first Spartan Race, I quickly realized that standard fitness trackers miss the complete picture. They tell you how many steps you took or how many hours you slept, but they don’t calculate readiness relative to high cognitive work combined with heavy physical output.

Step 1: The Notion Experiment

Before writing a single line of code, Ferrokinetic existed as a sprawling Notion workspace:

  • Daily fatigue tracking
  • Heart rate variability (HRV) logs
  • Cognitive load rating (1–10 scale)
  • Polar watch telemetry

While Notion worked as a manual prototype, the friction of manual data entry was too high. That was the spark: Why not build a dedicated training platform?

The Core Goal

  1. Automated Biometric Ingestion: OAuth 2.0 integration with Polar AccessLink API.
  2. Readiness Scoring: Balancing physical strain against software development load.
  3. Actionable Insights: Knowing when to push hard in training and when to prioritize recovery.

Stay tuned for BUILD_LOG_002, where I cover the transition from Notion databases to a React Native & Bun backend prototype.