Exercise 1: What Actually Ruled Out Caching — Possible Solution
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WHAT SPECIFICALLY RULED IT OUT
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Per this chapter (Step 2), a request made with response headers
visible showed "no X-Cache, no Age header, nothing indicating a cache
sits in front of this request." The absence of any cache-related
response header is the specific evidence that ruled caching out - if
a cache were involved, it would typically identify itself through
headers like these; their total absence means there is no cache layer
present at all to be the cause.

WHY "DIFFERENT USERS SEE DIFFERENT THINGS" WASN'T ENOUGH ON ITS OWN
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Per this chapter, that symptom pattern is described as "the classic
caching fingerprint" and "a genuinely reasonable first guess" - but a
symptom pattern only shows that a theory is PLAUSIBLE, not that it's
CONFIRMED. Other causes (as this chapter goes on to show) can produce
the exact same surface symptom - different users seeing different
content - for entirely different underlying reasons. The pattern
matching a known "shape" of problem doesn't prove that specific
mechanism is actually present in this case.

WHY THIS DISTINCTION MATTERS
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Per this chapter's own tip box, "a pattern match is a starting
hypothesis, not a diagnosis, until something in the logs actually
confirms it." Step 2 checked for the actual mechanism (cache headers)
that would have to exist for caching to be the real cause, rather than
concluding "it's probably caching" purely from the symptom matching a
familiar shape.

WHY THIS WORKS AS AN ANSWER
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It correctly identifies the absent cache headers as the specific
evidence that ruled out caching, and correctly explains why matching a
known symptom pattern is insufficient confirmation on its own.