The service provider that ran a query on every request

A settings lookup in a provider’s register() method, executed on every request including the ones that never read a setting.

// what it was
public function register(): void
{
    $this->app->singleton(Settings::class, fn () => new Settings(
        DB::table('settings')->pluck('value', 'key')->all()
    ));

    config(['app.timezone' => $this->app->make(Settings::class)->timezone()]);
    // ↑ this line resolves the singleton immediately
}

The binding was lazy and the line below it was not, which is the shape this mistake almost always takes — a closure that would never have run, forced by something that reads from it during boot. The 4 ms was not the problem; the problem was that it made the settings table part of the boot path, so a slow query there took down health checks that touched nothing else.