Skip to main content

> watch_045

The Cache Was Correct Yesterday

The Cache Was Correct Yesterday

Read full episode
The Cache Was Correct Yesterday Thumbnail

Available Video Versions

16:9
Default
9:16
Short
Watch on YouTube

The Cache Was Correct Yesterday

"The system failed exactly the way the roadmap trained it to fail."

What this episode is really about

The Pretend: cache invalidation, stale data, time-sensitive correctness, product truth.

What Actually Happened: The cache defended itself by explaining that it was completely correct yesterday.

Incident Type: Production Incident | Failure Pattern: cache invalidation drift

Technical takeaway

The Cache Was Correct Yesterday

How it appears in real teams

The Cache Was Correct Yesterday

What teams should watch for

Detection Signals:

  • Alerts firing

Prevention Checklist:

  • [ ] Test thoroughly
  • [ ] Review code

Premortem Questions: What happens if this breaks?

Postmortem Lessons: We should have tested this.

  • Test thoroughly
  • Review code

Transcript

Draft script (not verified video transcript)

Junior Developer: The customer sees yesterday’s price.
Cache Guy: Yesterday’s price was excellent.
Fetch: Today’s checkout disagrees.
Tiny CTO: Correctness has an expiration date when the business moves.
Cache Guy: I preserved the truth.
Tiny CTO: You preserved a truth with no freshness contract.
Junior Developer: So the cache was right and still wrong.
Cache Guy: Finally, someone respects my historical accuracy!

Frequently Asked Questions

What is the main theme of 'The Cache Was Correct Yesterday'?

The main theme is understanding how architectural compromises lead to predictable production incidents.

Who is the primary audience for this episode?

Software engineers, tech leads, and product managers who deal with system architecture and technical debt.

How can teams avoid the issues discussed?

By prioritizing system-wide context over local optimization and aligning incentives with long-term stability.

AI Summary

A TinyCTO.tv technical parable about cache invalidation, stale data, time-sensitive correctness, product truth. The episode shows that cached data must be judged against current truth, not historical accuracy.