fix(performance): fetch GitHub commits concurrently to prevent serverless timeouts

[nyxsky404]

This PR refactors the GitHub Search API pagination in fetchContributionsForAccount. Previously, the route fetched up to 10 pages sequentially in a while loop, which could take up to 20 seconds for highly active users and frequently caused 504 Gateway Timeouts on Vercel's edge/serverless architecture. The new implementation fetches the first page to determine the total_count, and then fetches the remaining required pages (up to 10 max) concurrently using Promise.all(). This drastically reduces the total execution time while correctly handling secondary rate limit (HTTP 429/403) fallbacks. Fixes #3170.

[github-actions]

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[Priyanshu-byte-coder]

Good instinct on the serverless timeout, but firing pages 2..N as fully-parallel Promise.all fans out up to ~9 concurrent GitHub Search calls on a single user token. GitHub's own guidance is explicit: "make requests for a single user serially… do not make them concurrently," and Search has a low secondary rate limit — a burst like this risks tripping a secondary-rate-limit block, which is worse than the sequential latency it replaces. Please cap concurrency to a small pool (2-3 at a time) instead of unbounded parallel, then I'll take another look. Also: rate-limited pages now silently drop their items — that's fine as partial results, just confirm that's intended.

[nyxsky404]

@Priyanshu-byte-coder

Updated:

• Capped concurrency for pages 2..N to a bounded pool of 3 at a time (matches the same pattern used in prs/route.ts's CONCURRENCY_BATCH), instead of firing all remaining pages via a single Promise.all. This keeps us within GitHub's guidance against concurrent requests on a single token while still avoiding the sequential-latency timeout.
• Confirmed: rate-limited pages intentionally return no items and the response falls back to whatever pages were already fetched, rather than failing the whole request. Added a comment in the code to make that explicit.
• Rebased onto latest main.

[Copilot]

Pull request overview

Refactors the GitHub commit Search API pagination in fetchContributionsForAccount to reduce latency and mitigate serverless/edge timeouts by fetching subsequent pages with bounded concurrency.

Changes:

• Adds a bounded concurrency approach for fetching additional GitHub Search pages after the first page determines total_count.
• Introduces PAGE_FETCH_CONCURRENCY to limit parallelism and reduce likelihood of triggering secondary rate limits.
• Restructures pagination from a sequential loop to batched Promise.all() calls.

Suppressed comments (1)

src/app/api/metrics/contributions/route.ts:225

• When a later page is rate-limited (or returns fewer than 100 items), the code currently keeps requesting subsequent batches. That can exacerbate secondary rate limits and adds unnecessary work; after a rate-limit response (or the first short page) you should stop issuing further page requests and just return the partial results collected so far.

        for (let i = 0; i < remainingPages.length; i += PAGE_FETCH_CONCURRENCY) {
          const batch = remainingPages.slice(i, i + PAGE_FETCH_CONCURRENCY);
          const batchResults = await Promise.all(batch.map((p) => fetchPage(p)));
          for (const res of batchResults) {
            // Rate-limited pages intentionally contribute no items; the

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[nyxsky404]

@Priyanshu-byte-coder Please review, repo is already stared by me