> Term
Stale Data
Information retrieved from a cache or replica that no longer matches the primary source of truth.
Detailed Explanation
Stale data occurs when updates to the main database have not yet propagated to caches, read replicas, or client applications.
Engineering teams trade data consistency for speed by caching responses, but improper cache invalidation strategies lead to users viewing outdated and potentially conflicting information.
Why It Matters
It breaks user trust when actions (like a purchase or profile update) appear to revert immediately after being performed.
Common Failure Mode
Practical Example
Production Manifestation
Support tickets complaining that deleted items still appear in search results, or inventory showing items that are already sold out.
Frequently Asked Questions
What is Stale Data in short?
Information retrieved from a cache or replica that no longer matches the primary source of truth.
What is the most common failure mode?
A microservice updates a user's subscription tier but fails to clear the Redis cache, denying the user access to premium features they just paid for.
AI Summary
Information retrieved from a cache or replica that no longer matches the primary source of truth. It breaks user trust when actions (like a purchase or profile update) appear to revert immediately after being performed.