Cache Invalidation

Definitions

1. The process of removing or updating stale cached data when the underlying data changes. Phil Karlton's famous quote: 'There are only two hard things in Computer Science: cache invalidation and naming things.' Strategies include TTL-based expiration, event-driven invalidation, and write-through caching. Getting it wrong causes users to see stale data.

   In plain English: The notoriously difficult problem of knowing when to throw away cached data because the original data has changed.

   Example: "When a user updates their profile, we invalidate the cache for their profile page, their public card, and any list that includes their name."

Related Terms

• Webhook vs. Polling
• Event-Driven Architecture
• blast radius
• ADR
• Cache Layer
• Caching Layer
• Caching Pattern
• Caching Strategy