docs(rate-limit): clarify KV-backed persistence vs in-memory fallback

[vipul674]

Related Issue

Closes #6207

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Documentation update (changes to documentation only)
• Refactor (code change that neither fixes a bug nor adds a feature)

Description

Improve documentation for and to clearly explain the dual-mode behavior:

• With KV configured: Rate limit state is persisted across restarts and shared across all serverless instances via atomic INCR + EXPIRE operations using Upstash Redis/Vercel KV.
• Without KV configured: Falls back to an in-memory TTL cache. State resets on cold start/server restart, but is effective at stopping aggressive single-instance spikes.

Changes

• : Updated JSDoc to document the KV-backed persistence mode and fallback behavior, with link to Upstash setup docs.
• : Added JSDoc documenting the in-memory limitation and recommending KV-backed alternatives for production.

Testing

• Documentation-only change, no code behavior modified
• Existing tests continue to pass

Checklist

• My code follows the project's style guidelines
• I have commented my code where necessary
• My changes generate no new warnings
• Any dependent changes have been merged and published

[vercel]

@vipul674 is attempting to deploy a commit to the jhasourav07's projects Team on Vercel.

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[github-actions]

📦 Next.js Bundle Size Report (Gzipped Sizes)

✨ No significant bundle size changes detected.

📊 Summary of Totals

Category	PR Size	Base Size	Difference
Total JS	3697.00 KB	3697.00 KB	0 B
Total CSS	296.58 KB	296.58 KB	0 B

[vipul674]

@JhaSourav07 Please Review.

[vipul674]

@JhaSourav07 I have submitted the fix. Please let me know if any changes are needed!

[Aamod-Dev]

Great work clearly documenting the behavior of our rate limiters. I appreciate that you've explicitly outlined the dual-mode in lib/rate-limit.ts and noted the serverless lifecycle limitations of RefreshRateLimiter in services/github/refresh-rate-limiter.ts. The link to the Upstash docs is a nice touch for developers looking to configure persistence. This improves the developer experience significantly. Approved!

[github-actions]

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