Exercise 3: Why force-unlock Requires Caution — Possible Solution
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`terraform force-unlock` exists specifically because a crash mid-apply
(the CI job dying, a network failure, a killed process) can leave a
lock record sitting in DynamoDB with no corresponding apply left to
ever release it -- since normal lock release only happens as part of
an apply finishing cleanly. Without some way to clear that orphaned
lock, every future apply would be permanently blocked by the "Error
acquiring the state lock" message the chapter shows, indefinitely.

The caution is warranted because force-unlock cannot actually tell the
difference between two situations that look identical from the
outside: (a) a lock left behind by something that has genuinely
crashed and will never finish, which is safe to clear, and (b) a lock
currently held by an apply that is simply still legitimately running --
a long apply provisioning many resources, for instance. Force-unlocking
case (b) would remove the lock while that apply is still actively
writing to state, opening the door to the EXACT concurrent-write
corruption locking exists to prevent in the first place (per Exercises
1 and 2) -- now potentially worse, since one of the two "concurrent"
writers is an apply that believes it still safely holds the lock.

What should be verified before running it: confirm, through means
outside Terraform's own locking mechanism (checking the CI system's
job history/logs, checking with teammates, checking whether the
process that acquired the lock is still actually running), that the
apply which took out the lock has genuinely terminated and is not
still in progress -- only then is clearing the lock actually safe.

WHY THIS WORKS AS AN ANSWER
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This explains the two situations force-unlock can't distinguish between
(a genuinely crashed process vs. a legitimately still-running one) and
why that ambiguity is exactly what makes it risky, then gives a
concrete verification step (checking external evidence the lock
mechanism itself can't provide) rather than a vague "be careful."