Exercise 1: Choosing a VM Family for an Idle-Then-Bursty Workload — Possible Solution
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The workload described -- mostly idle, with occasional short bursts of
real CPU-intensive work -- matches the B-family's own real CPU credit
model almost exactly. While the VM's actual usage stays below its own
baseline CPU performance level (the "mostly idle" periods), it
accumulates real credits. When the occasional burst of CPU-intensive
work happens, the VM spends those accumulated credits to run at
higher performance than its own baseline would normally allow.

A D-family or F-family VM, by contrast, would need to be sized for
the PEAK burst demand at all times, even though that peak only
happens occasionally -- meaning real money would be spent on
capacity that sits unused during every idle period in between bursts.

ANSWER: A B-family VM is the right recommendation. Its real CPU
credit mechanism directly fits this usage pattern: idle time builds
up credits, which are then spent automatically during the occasional
burst, letting the VM burst above its own base performance exactly
when needed without requiring a permanently larger, more expensive VM
size sized for peak demand around the clock.

WHY THIS WORKS AS AN ANSWER
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This correctly connects the specific real mechanism (credit
accumulation during idle time, credit spending during bursts) to the
specific real usage pattern described, rather than just naming
"B-series" as the answer without explaining why it fits -- and
explicitly rules out the alternative (a permanently larger VM)
by naming its real cost inefficiency for this exact pattern.