The Router

Another foundation axis — resolving a route's middleware. Unlike input() or config(), this is not a per-request multiplier: one request matches one route, and its middleware is resolved twice (dispatch + terminate). So the per-request saving is small in absolute terms — microseconds. What makes it worth a tier is that it's pure repeated waste removed on every request and every worker, and it compounds: with request volume, with worker count, and especially under Octane. There are two tiers, exactly as with config: a lazy per-router memo, and an eager, opcache-interned index that goes further.

What it does

For the matched route, Router::gatherRouteMiddleware() calls resolveMiddleware(), which: expands middleware groups and aliases through MiddlewareNameResolver, runs a map/flatten/values Collection chain, and then sorts via SortedMiddleware — which calls class_implements() + class_parents() on every middleware string to place it in the priority map. None of that is cached. The raw name list is memoized on the route (computedMiddleware), but the expand-and-sort that turns it into the final ordered class list runs every time — twice per request.

Tier 1 — the lazy memo. Grease\Routing\Router caches the exact resolved+sorted array, keyed by the literal (gathered, excluded) middleware-name signature. The output is a pure function of those names plus the process-constant alias/group/priority maps, so a repeat signature is a single hash hit. The order is load-bearing, so the array is cached verbatim — no reordering logic is touched.

Tier 2 — the eager index (grease:route-cache). Under FPM the router is rebuilt per request, so the lazy cache starts empty every request: the dispatch pass is always a cold miss, and only the terminate pass hits. The eager index removes that cold miss too. grease:route-cache is a drop-in twin of route:cache: it precomputes every route's resolved middleware and emits a sibling file holding a signature => [classes] map. Because that file is a constant return [...], opcache interns it into shared memory — require hands it back by reference, so every worker and request loads it for ~free, and the greased router's cache starts pre-seeded: both the dispatch and terminate passes are hits from request one.

route:cache is orthogonal, not the competition

route:cache caches URL matching (the compiled Symfony matcher) and the raw middleware names in each route's serialized action. It does not resolve or sort middleware — under route:cache, resolveMiddleware() still runs the full expand-and-sort on every matched request (verified against the framework source: the resolved/sorted list is never serialized, and there is no resolved-middleware cache anywhere in routing). The two stack: route:cache speeds up name → route, this speeds up names → resolved+sorted classes.

Does it stay correct when middleware changes?

Yes. Because the index keys by the same signature the lazy path uses, the eager tier is just a pre-seeded lazy cache — and both share one invalidation story:

• Every map mutator flushes the whole cache: aliasMiddleware, middlewareGroup, prependMiddlewareToGroup, pushMiddlewareToGroup, removeMiddlewareFromGroup, flushMiddlewareGroups. Laravel's own Kernel::syncMiddlewareToRouter() funnels all runtime middleware changes — priority included — back through aliasMiddleware/ middlewareGroup, so those flush too, seeded entries included.
• A seeded entry is served only on an exact signature match. A route whose middleware is assigned dynamically (or whose controller middleware varies) produces a different gathered list → a different key → a miss → live resolve. The eager index can never mask a route-content change; it can only ever return a build-time resolution for an identical signature.
• Live truth wins. Seeding is a union (+=), so an entry already resolved live this request is never overwritten by the index.

The carve-outs

• Lazy — direct map mutation. Writing $router->middlewarePriority = … (or ->middleware / ->middlewareGroups) directly instead of via the registration methods isn't observable. In practice this never bites: the only direct write Laravel does is in syncMiddlewareToRouter(), which immediately follows it with aliasMiddleware/middlewareGroup calls that flush — and it runs before dispatch, never mid-request.
• Eager — build must equal runtime. A hit returns the resolution computed at grease:route-cache time, so it's only valid if the alias/group/priority maps are the same when serving. The thing to avoid is gating middleware registration on the environment — a provider that registers middleware only for runningInConsole() (so the console build and HTTP serving disagree), or an env/flag-conditional alias such as throttle → Redis-vs-sync. Rebuild on every deploy, and the freshness guard handles the cached-artifact cases: the index loads only while it's at least as fresh as the route cache and the config cache, so a later route:cache, route:clear, config:cache, or php artisan optimize automatically disables a now-stale index (you fall back to the lazy memo — never served a wrong list). It is also inert in development: with no route cache present, the index never loads.

Under Octane vs FPM

The two tiers split cleanly, and it's the inverse of the config axis. Under Octane the router is a persistent singleton (Octane only re-points its container per request — verified: no listener mutates the middleware maps or flushes the cache), so the lazy memo already reaches its full value: every signature is resolved once for the worker's whole life. The eager index is the tier that wins FPM, where the router is per-request and the lazy cache can't survive between requests — the pre-seed makes both passes hits from a cold start. Together they bring FPM middleware resolution to ~Octane steady-state.

Behaviour-identical, by test

Parity is the resolved list and its order, asserted against vanilla Illuminate\Routing\Router across realistic stacks — the web/api groups, aliases, the priority map, exclusions, and duplicate names — on the cache miss, the cache hit, and after every alias/group mutation. The eager path adds: a seeded entry serves a hit equal to vanilla, a seed never overwrites a live entry, a map mutation flushes seeded entries, closures defer (no stable key), the command's var_export file round-trips, and the freshness-guard matrix (missing / newer / stale / route-clear / config-newer).

What it's worth

Don't expect a headline number on a single request — it's once-per-request work, so the delta is microseconds, dwarfed by the model/Blade/SQL tiers. The point is what it removes and where it compounds. Measured on Linux (benchmarks/docker, opcache + JIT): a single resolve is 6.8µs vanilla, and the lazy cache takes a repeat to 0.10µs (−98.5%). On the FPM-cold model (per request = dispatch + terminate resolve), vanilla is 13.1µs/request; the lazy tier roughly halves it to 6.8µs (it banks the terminate hit), and the eager index takes it to 0.25µs — −96% vs lazy, −98% vs vanilla, essentially eliminating middleware resolution as a request cost. That's ~13µs saved per request — invisible on one request, but pure waste removed on every one: multiply by your request rate and worker count. Under Octane the lazy tier alone gets there, as the cache persists.

Measure your own

These ratios are confirmed on Linux (benchmarks/route_cache_ab.php, middleware_ab.php, via benchmarks/docker, production-shaped opcache + JIT); the µs absolutes are for that box — reproduce on your target. macOS CLI inflates the absolutes (opcache off), but the ratios hold.

Memory

The lazy cache is a small array bounded by the number of distinct route signatures (a few dozen, typically) — no per-request growth, no leak. The eager index is one constant array that lives once in opcache shared memory, shared across every worker and request, so its per-request heap cost is ~nil.

Opt in

The greased router is wired into the HTTP kernel by constructor injection before any provider runs, so — unlike the event/view/config rebinds — a provider can't install it (the kernel keeps its own reference). Swap it where the binding is first defined, in bootstrap/app.php, before the kernel resolves:

$app = Application::configure(basePath: dirname(__DIR__))
    ->withRouting(/* … */)
    ->withMiddleware(/* … */)
    ->create();

Grease\Routing\Router::swap($app);   // the lazy tier

return $app;

That's the whole lazy tier, and it carries no real caveat — take it anywhere. For the eager index, register the provider and swap route:cache for grease:route-cache in your deploy:

// bootstrap/providers.php
Grease\Routing\GreaseRoutingServiceProvider::class,

php artisan grease:route-cache   # route:cache + the opcache-interned middleware index

Run it last in your deploy (it runs route:cache itself), so a later route:cache/optimize doesn't shadow it. Without the swap, or without a fresh index, the provider is inert — the lazy memo still applies.