Exercise 2: MemoryHigh= vs. MemoryMax= — The Real Difference — Possible Solution
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Explanation:

Per the chapter's own compare-table, these two settings trigger
genuinely different kernel responses, not just different numeric
thresholds of the same underlying behavior.

Exceeding MemoryHigh= triggers what the chapter describes as a SOFT
response -- "throttling and reclaim pressure encouraged, no kill." The
service is still allowed to keep running and keep using memory beyond
this threshold if it genuinely needs to, but the kernel actively
applies backpressure, encouraging the process to free up memory it
isn't actively using, and may slow it down somewhat in the process.
Critically, per the chapter's own table, no process is killed as a
direct result of crossing MemoryHigh= alone -- it's a pressure signal,
not a hard boundary.

Exceeding MemoryMax=, by contrast, triggers a HARD response -- per the
chapter's own table, "the cgroup-scoped OOM killer triggers." This is
a genuine kill event: the kernel's out-of-memory killer activates
specifically within this service's own cgroup (not searching the
whole system for an arbitrary victim, per the chapter's own earlier
explanation), terminating the offending process rather than merely
throttling it. There's no negotiation or gradual pressure at this
point -- crossing MemoryMax= means the process gets killed.

The practical relationship between the two: MemoryHigh= is meant to
sit BELOW MemoryMax= as an early-warning, gentler intervention,
giving a well-behaved service a chance to reduce its own memory
footprint before ever reaching the hard MemoryMax= ceiling where it
would actually be killed outright.

WHY THIS WORKS AS AN ANSWER
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This distinguishes the two settings by their actual kernel-level
consequence (throttling pressure vs. an actual kill), directly quoting
the chapter's own compare-table language, rather than treating them as
merely two different numeric thresholds for the same action.