perf(webapp): memoize react-router per-request route matching via pnpm patch by ericallam · Pull Request #3877 · triggerdotdev/trigger.dev

ericallam · 2026-06-09T15:00:24Z

Summary

Under high request load the webapp spends most of its CPU inside react-router's matchRoutes, not in application code. @remix-run/router@1.23.2 (the React Router v6 / Remix 2 core) re-flattens, re-ranks, and recompiles the entire route table on every request, and with the webapp's ~436 routes that cost dominates once request rates climb. There is no NODE_ENV gate, so production pays it too.

This adds a pnpm patch that memoizes the parts that depend only on the static route manifest: it caches the flattened/ranked branches per route tree, hoists the loop-invariant decodePath out of the match loop, and caches compiled path regexes.

Benchmark

CPU profile over the same load (100 concurrent tag feeds, ~425 req/s), NODE_ENV=production, before vs after the patch:

Metric	Before	After
Active CPU (self-time over the window)	28.3s	18.5s (-34%)
Route-matching self-time	19.2s	7.5s (-61%)
Event-loop lag p99	322ms	113ms (-65%)
Idle headroom	26%	52%

Application/realtime code was ~0% of CPU in both profiles; the bottleneck was entirely generic per-request route matching.

Why a patch instead of an upgrade

The inefficiency is acknowledged upstream (remix-run/react-router#8653). A contributor PR doing exactly this (remix-run/react-router#14866) was closed in favor of a narrower fix (remix-run/react-router#14967, branch caching only, shipped in React Router v7), with the maintainer suggesting patch-package as the interim until the Remix 3 route-pattern rewrite (see remix-run/remix#4786). We are on the v6-era core and cannot pick up even the partial fix without a framework migration, so this patch is the sanctioned stopgap, and it also includes the compiled-regex cache the merged PR left out.

patches/README.md documents the full rationale, the safety argument (deterministic, internal-only, bounded caches), and when to remove the patch.

…m patch react-router's matchRoutes re-flattened, re-ranked, and recompiled the entire route table on every request. With the webapp's ~436 routes that cost dominates once request rates climb, and there is no NODE_ENV gate so production pays it too. Patch @remix-run/router to memoize the work that depends only on the static route manifest: cache flattened/ranked branches per route tree, hoist the loop-invariant path decode out of the match loop, and cache compiled path regexes. On a local benchmark this cut route-matching CPU by roughly 60% and halved event-loop lag under load. See patches/README.md for the upstream history (react-router#14866 / #14967) and when to drop the patch.

changeset-bot · 2026-06-09T15:00:28Z

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coderabbitai · 2026-06-09T15:00:48Z

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.server-changes/react-router-route-matching-perf.md
package.json
patches/@remix-run__router@1.23.2.patch
patches/README.md

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🧠 Learnings (1)

📚 Learning: 2026-05-14T14:54:39.095Z

Learnt from: ericallam
Repo: triggerdotdev/trigger.dev PR: 3545
File: .server-changes/agent-view-sessions.md:10-10
Timestamp: 2026-05-14T14:54:39.095Z
Learning: In the `trigger.dev` repository, do not flag inconsistent dot vs slash notation in route/path strings inside `.server-changes/*.md` files. These markdown files are consumed verbatim into the changelog, so the mixed notation (e.g., `resources.orgs.../runs.$runParam/...`) is intentional and should be preserved as-is.

Applied to files:

.server-changes/react-router-route-matching-perf.md

🪛 LanguageTool

patches/README.md

[grammar] ~72-~72: Ensure spelling is correct
Context: ...w algorithm instead of trying to > band-aide perf improvements to the existing algor...

(QB_NEW_EN_ORTHOGRAPHY_ERROR_IDS_1)

[grammar] ~94-~94: Ensure spelling is correct
Context: ...build (dist/router.cjs.js), which the webapp server loads at runtime (`@remix-run/...

(QB_NEW_EN_ORTHOGRAPHY_ERROR_IDS_1)

[grammar] ~99-~99: Ensure spelling is correct
Context: ... to remove Drop this patch if/when the webapp moves to React Router v7+ (which thread...

(QB_NEW_EN_ORTHOGRAPHY_ERROR_IDS_1)

🔇 Additional comments (4)

patches/@remix-run__router@1.23.2.patch (1)

1-69: LGTM!

package.json (1)

89-90: LGTM!

patches/README.md (1)

1-102: LGTM!

.server-changes/react-router-route-matching-perf.md (1)

1-6: LGTM!

Walkthrough

This PR adds a performance optimization patch for react-router's route matching logic. The patch introduces three caching strategies: a WeakMap-based cache for flattened and ranked route branches per routes tree reference, hoisting of path decoding to avoid repeated decoding per branch, and a Map-based cache for compiled path patterns keyed by pattern parameters with a size guard at 2000 entries. The patch is registered in package.json's pnpm.patchedDependencies, with supporting documentation in patches/README.md explaining the optimization rationale and safety assumptions, plus a changelog entry recording the improvement.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Description check	❓ Inconclusive	The description provides comprehensive technical context, benchmarks, rationale, and upstream links, but does not follow the repository's required template structure with explicit checklist, testing, and changelog sections.	Reformat the description to match the repository template: add the explicit checklist items, dedicated Testing section, and Changelog section, while preserving the detailed technical content.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title directly and clearly summarizes the main change: memoizing react-router's per-request route matching via a pnpm patch to improve webapp performance.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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ericallam marked this pull request as ready for review June 9, 2026 16:58

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perf(webapp): memoize react-router per-request route matching via pnpm patch#3877

perf(webapp): memoize react-router per-request route matching via pnpm patch#3877
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ericallam commented Jun 9, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Summary

Benchmark

Why a patch instead of an upgrade

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ericallam commented Jun 9, 2026 •

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