bump threshold to 0.6 for production

[shixiao-coder]

Bumping to fully using threshold of 0.6 after discussed offline with Dave and Gabe

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request updates the production configuration to increase the rollout percentage for a specific feature flag. This change is part of a planned phased deployment to expand the availability of the SPANNER_EMBEDDING_THRESHOLD feature to 50% of production traffic.

Highlights

• Feature Flag Rollout: Increased the rollout percentage for the SPANNER_EMBEDDING_THRESHOLD feature flag from 20% to 50% in the production environment.

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[github-actions]

⚠️ PRODUCTION FEATURE FLAG CHANGE — REVIEW CHECKLIST

Please conduct a careful review before merging this production change & coordinate with the oncaller.
Merging this PR will trigger a rolling restart of all Kubernetes pods in production.

Things to check before approving:

• Staging Validated: Have these exact flag changes been tested and verified in staging?
• Cache Invalidation: If API responses change, remember to clear the Redis cache after merging.
• Time Window: Ensure updates occur during global working hours; request lead approval for Friday–Sunday updates.
• Oncall Communication: Please additionally announce this update on the oncall thread.
• Type Safety: Verify that flag value types match what the server binary expects.

[gemini-code-assist]

Code Review

This pull request increases the rollout percentage for the use_config_threshold_for_spanner_embedding feature flag from 20% to 50% in production. The reviewer noted that because the feature flag evaluation uses non-sticky random assignment, a fractional rollout percentage can lead to inconsistent behavior if evaluated multiple times within a single request. They suggest implementing sticky cohort assignment or caching the flag's value per request context.

[gmechali]

Thanks Xiao!