The Golden Rule: When NOT to Cache

Imagine you just sent $100 to your friend through a banking app. Your friend calls excitedly: "Thanks for the money!" But when you check your account balance, it still shows the old amount. You panic: "Did the transfer fail?"

This nightmare scenario happens when banks cache account balances. Some data is too important to be stale.

The Staleness Problem: Caching means serving potentially outdated information. While this is fine for a website logo (who cares if it's 5 minutes old?), it's catastrophic for:

• Bank account balances
• Stock prices
• Medical records
• Real-time inventory counts

Pro Tip: If being wrong for even a few seconds could cause problems, don't cache it. Consistency trumps speed for critical data.

Caching is like having a smart assistant who remembers things for you - incredibly helpful, but you wouldn't want them giving outdated information about your bank balance!