> Term
hidden dependency
An undocumented or unmanaged reliance between system components that only reveals itself when it fails.
Detailed Explanation
An undocumented or unmanaged reliance between two parts of a system that is completely invisible on official architecture diagrams.
It lurks quietly in the background until the upstream component changes or fails, instantly breaking the downstream component in deeply confusing ways.
Why It Matters
They make systems fragile, unpredictable, and significantly prolong incident resolution times because the root cause is invisible to the responding engineers.
Common Failure Mode
Practical Example
Production Manifestation
Scripts reading directly from another service's private database, undocumented cron jobs, or shared API tokens that are hardcoded.
Frequently Asked Questions
What is hidden dependency in short?
An undocumented or unmanaged reliance between system components that only reveals itself when it fails.
What is the most common failure mode?
A team deletes an 'unused' internal API endpoint, suddenly taking down the billing system because a legacy reporting script secretly relied on it for five years.
AI Summary
An undocumented or unmanaged reliance between system components that only reveals itself when it fails. They make systems fragile, unpredictable, and significantly prolong incident resolution times because the root cause is invisible to the responding engineers.