Exercise 3: The Real Mistake This Chapter Warns Against — Possible Solution
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WHY CACHING BEING "REASONABLE" WASN'T THE PROBLEM
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Per this chapter's own tip box, "caching was a genuinely reasonable
first guess - the symptom pattern really does match how caching
problems usually look." The chapter explicitly does NOT criticize
forming that hypothesis - having a reasonable starting theory based on
a familiar symptom pattern is treated as normal and expected, not a
mistake in itself.

THE ACTUAL MISTAKE THIS CHAPTER WARNS AGAINST
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Per this chapter, "the discipline that mattered here wasn't avoiding
that guess, it was refusing to stop at it without checking." The real
mistake would have been treating the plausible guess as if it were
already confirmed - acting on "it's probably caching" without actually
verifying it against real evidence (the cache headers), and potentially
spending time and effort "fixing" a cache that was never actually
involved.

WHY THIS DISTINCTION MATTERS PRACTICALLY
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Per this chapter, "a pattern match is a starting hypothesis, not a
diagnosis, until something in the logs actually confirms it." Skipping
Steps 2 and 3's verification and jumping straight to "it's caching, fix
the cache" would have left the real cause (the incomplete deployment
to backend-1) completely undiscovered and unfixed, even after time was
spent addressing a cache that didn't exist.

WHY THIS WORKS AS AN ANSWER
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It correctly distinguishes forming a reasonable hypothesis (fine, even
expected) from treating an unverified hypothesis as a confirmed
diagnosis (the actual mistake), using this chapter's own explicit
framing of what the real lesson was.