Smooth GC capacity alarms with a severe-pressure fast path

[stopachka]

Use three of five one-minute GC maxima above 10% to add capacity, with a separate alarm for two consecutive maxima above 15%. Both alarms use the existing scale-up policy. CPU, heap, metric dimensions, missing-data handling, and scale-in settings retain their current values.

This PR targets the current production configuration branch so its diff contains only the GC alarm change. Application code and the immutable application image are unchanged.

Validation: parsed the YAML and checked that all other options/resources are identical; exercised eight threshold and burst examples; replayed 40 complete saved minute bins as an offline predicate check. The replay does not simulate CloudWatch's missing-data lookback, publication delay, or policy execution, and does not establish that the prior scale-out was unnecessary. No production update was performed for this PR.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Configuration used: Repository UI

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Plan: Advanced

Run ID: da4cba94-d187-4d79-88fc-2732d88a8d62

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Reviewing files that changed from the base of the PR and between df03d8c and cf4157c.

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• server/.ebextensions/resources.config

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📝 Walkthrough

Walkthrough

The GC scaling alarm now detects pauses above 10% in three of five minutes. A new severe-GC alarm detects pauses above 15% in two consecutive minutes. The high-GC alarm explicitly targets the scale-up policy.

Changes

GC Alarm Controls

Layer / File(s)	Summary
Alarm thresholds and scaling configuration server/.ebextensions/resources.config	InstantHighGcAlarm now uses five evaluation periods and requires three breaching datapoints. Its description states the 10% threshold. The alarm targets the scale-up policy. InstantSevereGcAlarm monitors 15% GC pauses across two minutes.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Feature

Merge Risk: ⚪ Minimal · up to cf415

The GC alarms match the intended thresholds and scaling configuration, with no unresolved merge-blocking concerns.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: smoother GC capacity alarms with a separate severe-pressure fast path.
Description check	✅ Passed	The description directly explains the GC alarm thresholds, scale-up behavior, preserved settings, validation, and deployment scope.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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