fix(cache): make in memory cache global

[MasterPtato]

Description

Please include a summary of the changes and the related issue. Please also include relevant motivation and context.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

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Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[railway-app]

🚅 Deployed to the rivet-pr-4560 environment in rivet-frontend

Service	Status	Web	Updated (UTC)
kitchen-sink	❌ Build Failed (View Logs)	Web	Apr 7, 2026 at 1:31 am
mcp-hub	✅ Success (View Logs)	Web	Apr 5, 2026 at 7:25 pm
website	❌ Build Failed (View Logs)	Web	Apr 5, 2026 at 7:25 pm
frontend-cloud	❌ Build Failed (View Logs)	Web	Apr 5, 2026 at 7:24 pm
ladle	❌ Build Failed (View Logs)	Web	Apr 5, 2026 at 7:24 pm
frontend-inspector	❌ Build Failed (View Logs)	Web	Apr 5, 2026 at 7:24 pm

[MasterPtato]

• chore: remove non-engine drivers #4574 : 2 dependent PRs (#4581 , #4582 )
• feat: dynamic actors #4397
• fix: driver test suite & sqlite reliability #4559
• fix: remove serverless token #4572
• fix: misc token fixes #4569
• fix(pb): clean up actor stop decision handling #4566
• fix(envoy): use global instance, add signal handlers #4565
• chore: misc fixes, add pb snapshot test #4561
• fix(cache): make in memory cache global #4560 👈 (View in Graphite)
• main

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[claude]

PR Review: fix(cache): make in memory cache global. Summary: The PR makes the in-memory cache and in-flight map global singletons using OnceLock. The tracing improvements are clean. Issues: (1) Silent capacity mismatch in InMemoryDriver::new (driver.rs:147) - After the first call to InMemoryDriver::new(max_capacity), the max_capacity argument is silently ignored by subsequent calls since OnceLock::get_or_init is a no-op after initialization. Consider removing max_capacity entirely or asserting it matches on subsequent calls. (2) Test isolation risk - Both CACHE and IN_FLIGHT are process-level statics. Tests creating multiple InMemoryDriver or CacheInner instances share the same underlying state, so state from one test can leak into another. (3) Shared IN_FLIGHT across CacheInner instances (inner.rs:51) - If multiple CacheInner instances are created for different subsystems, they share the same in-flight map. A comment documenting this assumption would help future readers. Positives: Empty check before cache.driver.get() avoids a no-op round-trip; tracing improvements are cleaner; eviction listener is useful for observability. Minor: InMemoryDriver is now an empty struct and could be a ZST.