perf: dedupe getShared with React cache and parallelize updates page fetches

[hugodemenez]

Problem

Two performance issues in the Next.js pages:

1. Shared page (/shared/[slug]) — getShared(slug) was called twice per request: once in generateMetadata and again in the page component. Since getShared runs a Prisma transaction that queries the DB for trades, tick details, and groups (and also increments the view counter), the duplicate call doubled both latency and cost per page load, and inflated view counts.

2. Updates page (/updates/[slug]) — getPost and getAdjacentPosts are independent data fetches but were running sequentially, adding unnecessary latency.

Solution

Shared page — React cache() deduplication

Wrapped getShared with React's cache() at module scope (getCachedShared). React cache deduplicates calls with the same arguments within a single server render, so generateMetadata and the page component now share a single DB call.

Updates page — Promise.allSettled parallelization

Replaced the sequential await getPost() / await getAdjacentPosts() with Promise.allSettled([...]) so both fetches run concurrently. allSettled preserves the existing error-handling behavior: a failed getAdjacentPosts gracefully falls back to { previous: null, next: null } without blocking the page render.

Changed files

• app/[locale]/shared/[slug]/page.tsx
• app/[locale]/(landing)/updates/[slug]/page.tsx

  

[vercel]

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Project	Deployment	Actions	Updated (UTC)
deltalytix	Ready	Preview, Comment	May 2, 2026 9:59pm

[github-actions]

🤖 Automated Code Review

Here is a concise review based on /home/runner/work/deltalytix/deltalytix/pr.diff.

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PR review summary

Updates page (updates/[slug]/page.tsx)

Good

• Parallel I/O: Promise.allSettled runs getPost and getAdjacentPosts together, which should shorten time-to-render when both succeed.
• Failures: Main post rejects → still matches prior behavior (console.error + notFound()). Adjacent rejects → still falls back to { previous: null, next: none }.

Considerations

• Behavior under main-post failure: Before, adjacent posts were fetched only after a successful getPost. Now both run every time. If getPost rejects or resolves to “not found” quickly, you may still complete an unnecessary getAdjacentPosts call. Usually a minor cost; worth confirming that’s acceptable.
• Readability: The IIFE around the rejection branch works but is heavier than a small let + if/else or a helper—pure style.

No security or correctness issues jumped out from the diff alone.

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Shared page (shared/[slug]/page.tsx)

Good

• cache(getShared) is appropriate for deduping the same slug between generateMetadata and the page in one request, avoiding duplicate work—a common Next.js/React pattern.

Minor

• No newline at end of file: The diff removes the final newline; worth restoring for POSIX/tooling consistency.

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TypeScript / React / errors

• Types: Explicit cast on the adjacent fallback matches the earlier “make TS happy” pattern; acceptable if getAdjacentPosts’ return type isn’t inferred as { previous; next } already.
• Error handling: Unchanged versus the old shared page component (still no local try/catch around the page fetch); metadata still catches and logs errors for metadata-only failures.

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Verdict

• Critical issues: None identified from this diff alone.

• Main follow-ups: Optional—avoid extra adjacent fetch when the post cannot load (restore sequential or short-circuit if that matters operationally); restore EOF newline on shared/[slug]/page.tsx.

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  Generated by Cursor CLI workflow

[Copilot]

Pull request overview

This PR targets server-render performance in two Next.js App Router pages by reducing redundant data-fetch work and improving fetch concurrency.

Changes:

• Deduplicates /shared/[slug] data fetching by wrapping getShared with React cache() so generateMetadata and the page reuse the same request-scoped result.
• Parallelizes /updates/[slug] fetching of the main post and adjacent navigation data using Promise.allSettled.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
app/[locale]/shared/[slug]/page.tsx	Adds a cached wrapper around getShared and uses it in both generateMetadata and the page component to avoid duplicate DB work / double view increments.
app/[locale]/(landing)/updates/[slug]/page.tsx	Runs getPost and getAdjacentPosts concurrently to reduce end-to-end latency of the updates page render.

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