Optimize frontend: memoization, modern React hooks, reduced render overhead

- useTimeAgo: replace per-instance intervals with shared useSyncExternalStore ticker
- useTiltEffect: gate to fine-pointer devices, skip motion graphs on touch
- Carousel: bake WheelGesturesPlugin into primitive, remove from all consumers
- TitleSeasons: use memoized Set + precomputed progress map instead of Array.includes
- useSearch: stabilize results identity with useMemo
- CommandPalette: hoist shortcut grouping to module scope, stabilize effect deps
- StarRating: hoist static spring transition to module constant
- Settings toggles: use useOptimistic + useTransition for auto-rollback

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/(pages)/dashboard/_components/continue-watching-list.tsx

@@ -1,6 +1,5 @@
 "use client";
 
-import { WheelGesturesPlugin } from "embla-carousel-wheel-gestures";
 import {
   Carousel,
   CarouselContent,
@@ -19,7 +18,6 @@ export function ContinueWatchingList({
   return (
     <Carousel
       opts={{ align: "start", dragFree: true, containScroll: "trimSnaps" }}
-      plugins={[WheelGesturesPlugin({ forceWheelAxis: "x" })]}
       className="-mx-4 sm:-mx-0"
     >
       <CarouselContent className="px-4 sm:px-0">

app/(pages)/explore/_components/filterable-title-row.tsx

@@ -1,6 +1,5 @@
 "use client";
 
-import { WheelGesturesPlugin } from "embla-carousel-wheel-gestures";
 import { createStore, Provider, useAtom, useAtomValue } from "jotai";
 import { useState } from "react";
 import { TitleCardSkeleton } from "@/components/skeletons";
@@ -162,7 +161,6 @@ function FilterableTitleRowInner({
               dragFree: true,
               containScroll: "trimSnaps",
             }}
-            plugins={[WheelGesturesPlugin({ forceWheelAxis: "x" })]}
             className="-mx-6 sm:-mx-2 carousel-tilt"
           >
             <CarouselContent className="px-6 sm:px-2">

app/(pages)/explore/_components/title-row.tsx

@@ -1,6 +1,5 @@
 "use client";
 
-import { WheelGesturesPlugin } from "embla-carousel-wheel-gestures";
 import { TitleCard } from "@/components/title-card";
 import {
   Carousel,
@@ -44,7 +43,6 @@ export function TitleRow({
       </div>
       <Carousel
         opts={{ align: "start", dragFree: true, containScroll: "trimSnaps" }}
-        plugins={[WheelGesturesPlugin({ forceWheelAxis: "x" })]}
         className="-mx-6 sm:-mx-2 carousel-tilt"
       >
         <CarouselContent className="px-6 sm:px-2">

app/(pages)/settings/_components/registration-section.tsx

@@ -1,7 +1,7 @@
 "use client";
 
 import { IconDoorEnter } from "@tabler/icons-react";
-import { useState } from "react";
+import { useOptimistic, useState, useTransition } from "react";
 import { toast } from "sonner";
 import { CardContent, CardDescription, CardTitle } from "@/components/ui/card";
 import { Switch } from "@/components/ui/switch";
@@ -15,21 +15,20 @@ export function RegistrationSection({
   const [registrationOpen, setRegistrationOpen] = useState(
     initialRegistrationOpen,
   );
-  const [toggling, setToggling] = useState(false);
+  const [optimisticOpen, setOptimisticOpen] = useOptimistic(registrationOpen);
+  const [isPending, startTransition] = useTransition();
 
-  async function handleToggle(checked: boolean) {
-    const previous = registrationOpen;
-    setRegistrationOpen(checked);
-    setToggling(true);
-    try {
-      await toggleRegistration(checked);
-      toast.success(checked ? "Registration opened" : "Registration closed");
-    } catch {
-      setRegistrationOpen(previous);
-      toast.error("Failed to update registration setting");
-    } finally {
-      setToggling(false);
-    }
+  function handleToggle(checked: boolean) {
+    startTransition(async () => {
+      setOptimisticOpen(checked);
+      try {
+        await toggleRegistration(checked);
+        setRegistrationOpen(checked);
+        toast.success(checked ? "Registration opened" : "Registration closed");
+      } catch {
+        toast.error("Failed to update registration setting");
+      }
+    });
   }
 
   return (
@@ -47,9 +46,9 @@ export function RegistrationSection({
           </div>
         </div>
         <Switch
-          checked={registrationOpen}
+          checked={optimisticOpen}
           onCheckedChange={handleToggle}
-          disabled={toggling}
+          disabled={isPending}
           aria-label="Toggle open registration"
         />
       </div>

app/(pages)/settings/_components/update-check-section.tsx

@@ -1,7 +1,7 @@
 "use client";
 
 import { IconWorldUpload } from "@tabler/icons-react";
-import { useState } from "react";
+import { useOptimistic, useState, useTransition } from "react";
 import { toast } from "sonner";
 import { CardContent, CardDescription, CardTitle } from "@/components/ui/card";
 import { Switch } from "@/components/ui/switch";
@@ -13,23 +13,22 @@ export function UpdateCheckSection({
   initialEnabled: boolean;
 }) {
   const [enabled, setEnabled] = useState(initialEnabled);
-  const [toggling, setToggling] = useState(false);
+  const [optimisticEnabled, setOptimisticEnabled] = useOptimistic(enabled);
+  const [isPending, startTransition] = useTransition();
 
-  async function handleToggle(checked: boolean) {
-    const previous = enabled;
-    setEnabled(checked);
-    setToggling(true);
-    try {
-      await toggleUpdateCheck(checked);
-      toast.success(
-        checked ? "Update checks enabled" : "Update checks disabled",
-      );
-    } catch {
-      setEnabled(previous);
-      toast.error("Failed to update setting");
-    } finally {
-      setToggling(false);
-    }
+  function handleToggle(checked: boolean) {
+    startTransition(async () => {
+      setOptimisticEnabled(checked);
+      try {
+        await toggleUpdateCheck(checked);
+        setEnabled(checked);
+        toast.success(
+          checked ? "Update checks enabled" : "Update checks disabled",
+        );
+      } catch {
+        toast.error("Failed to update setting");
+      }
+    });
   }
 
   return (
@@ -50,9 +49,9 @@ export function UpdateCheckSection({
           </div>
         </div>
         <Switch
-          checked={enabled}
+          checked={optimisticEnabled}
           onCheckedChange={handleToggle}
-          disabled={toggling}
+          disabled={isPending}
           aria-label="Toggle automatic update checks"
         />
       </div>

app/(pages)/titles/[id]/_components/cast-carousel.tsx

@@ -1,7 +1,6 @@
 "use client";
 
 import { IconUser, IconUsers } from "@tabler/icons-react";
-import { WheelGesturesPlugin } from "embla-carousel-wheel-gestures";
 import Image from "next/image";
 import Link from "next/link";
 import {
@@ -31,7 +30,6 @@ export function CastCarousel({ actors, titleType }: CastCarouselProps) {
             dragFree: true,
             containScroll: "trimSnaps",
           }}
-          plugins={[WheelGesturesPlugin({ forceWheelAxis: "x" })]}
           className="-mx-4 sm:-mx-0"
         >
           <CarouselContent className="px-4 sm:px-0">

app/(pages)/titles/[id]/_components/star-rating.tsx

@@ -4,6 +4,12 @@ import { IconStar, IconStarFilled } from "@tabler/icons-react";
 import { motion } from "motion/react";
 import { useState } from "react";
 
+const springTransition = {
+  type: "spring" as const,
+  stiffness: 400,
+  damping: 15,
+};
+
 interface StarRatingProps {
   value: number;
   onChange: (value: number) => void;
@@ -36,11 +42,7 @@ export function StarRating({ value, onChange }: StarRatingProps) {
             animate={
               filled && star === value ? { scale: [1, 1.25, 1] } : { scale: 1 }
             }
-            transition={{
-              type: "spring" as const,
-              stiffness: 400,
-              damping: 15,
-            }}
+            transition={springTransition}
           >
             {filled ? (
               <IconStarFilled className="size-4.5 text-primary" />

app/(pages)/titles/[id]/_components/title-seasons.tsx

@@ -11,7 +11,7 @@ import { format, parseISO } from "date-fns";
 import { useAtomValue, useSetAtom } from "jotai";
 import { AnimatePresence, motion } from "motion/react";
 import Image from "next/image";
-import { useEffect, useState } from "react";
+import { useEffect, useMemo, useState } from "react";
 import {
   AlertDialog,
   AlertDialogAction,
@@ -50,6 +50,7 @@ export function TitleSeasons({
 
   const seasons = useAtomValue(seasonsAtom);
   const episodeWatches = useAtomValue(episodeWatchesAtom);
+  const watchedSet = useMemo(() => new Set(episodeWatches), [episodeWatches]);
   const userStatus = useAtomValue(userStatusAtom);
   const watchingEp = useAtomValue(watchingEpAtom);
   const {
@@ -58,6 +59,18 @@ export function TitleSeasons({
     handleUnmarkSeason,
     handleMarkAllWatched,
   } = useTitleActions();
+  const seasonProgress = useMemo(() => {
+    const map = new Map<string, number>();
+    for (const season of seasons) {
+      let count = 0;
+      for (const ep of season.episodes) {
+        if (watchedSet.has(ep.id)) count++;
+      }
+      map.set(season.id, count);
+    }
+    return map;
+  }, [seasons, watchedSet]);
+
   const [openSeason, setOpenSeason] = useState<number | null>(null);
   const [markAllOpen, setMarkAllOpen] = useState(false);
 
@@ -110,9 +123,7 @@ export function TitleSeasons({
       <div className="space-y-2">
         {seasons.map((season) => {
           const isOpen = openSeason === season.seasonNumber;
-          const watchedCount = season.episodes.filter((ep) =>
-            episodeWatches.includes(ep.id),
-          ).length;
+          const watchedCount = seasonProgress.get(season.id) ?? 0;
           const totalCount = season.episodes.length;
           const progressPercent =
             totalCount > 0 ? (watchedCount / totalCount) * 100 : 0;
@@ -207,7 +218,7 @@ export function TitleSeasons({
                     className="overflow-hidden border-t border-border/50"
                   >
                     {season.episodes.map((ep) => {
-                      const isWatched = episodeWatches.includes(ep.id);
+                      const isWatched = watchedSet.has(ep.id);
                       const { stillPath } = ep;
                       return (
                         <div

components/command-palette.tsx

@@ -44,6 +44,15 @@ import {
 } from "@/lib/atoms/command-palette";
 import { SHORTCUT_DESCRIPTIONS } from "@/lib/constants/shortcuts";
 
+const groupedShortcuts: Record<
+  string,
+  { description: string; keys: readonly string[] }[]
+> = {};
+for (const entry of SHORTCUT_DESCRIPTIONS) {
+  if (!groupedShortcuts[entry.scope]) groupedShortcuts[entry.scope] = [];
+  groupedShortcuts[entry.scope].push(entry);
+}
+
 type SearchResult = ReturnType<typeof useSearch>["results"][number];
 
 export function CommandPalette() {
@@ -102,7 +111,7 @@ export function CommandPalette() {
     return () => {
       if (saveTimerRef.current) clearTimeout(saveTimerRef.current);
     };
-  }, [debouncedQuery, results, setRecentSearches]);
+  }, [debouncedQuery, results.length, setRecentSearches]);
 
   const handleSelect = useCallback(
     (result: SearchResult) => {
@@ -134,16 +143,6 @@ export function CommandPalette() {
 
   const hasQuery = query.trim().length > 0;
 
-  // Group shortcuts by scope for help dialog
-  const grouped: Record<
-    string,
-    { description: string; keys: readonly string[] }[]
-  > = {};
-  for (const entry of SHORTCUT_DESCRIPTIONS) {
-    if (!grouped[entry.scope]) grouped[entry.scope] = [];
-    grouped[entry.scope].push(entry);
-  }
-
   return (
     <>
       <Dialog open={commandPaletteOpen} onOpenChange={setCommandPaletteOpen}>
@@ -362,7 +361,7 @@ export function CommandPalette() {
             <DialogTitle>Keyboard Shortcuts</DialogTitle>
           </DialogHeader>
           <div className="space-y-5 py-2">
-            {Object.entries(grouped).map(([scope, items]) => (
+            {Object.entries(groupedShortcuts).map(([scope, items]) => (
               <div key={scope} className="space-y-2">
                 <h3 className="text-[10px] font-semibold uppercase tracking-wider text-muted-foreground">
                   {scope}

components/ui/carousel.tsx

@@ -4,10 +4,13 @@ import { IconChevronLeft, IconChevronRight } from "@tabler/icons-react";
 import useEmblaCarousel, {
   type UseEmblaCarouselType,
 } from "embla-carousel-react";
+import { WheelGesturesPlugin } from "embla-carousel-wheel-gestures";
 import * as React from "react";
 import { Button } from "@/components/ui/button";
 import { cn } from "@/lib/utils";
 
+const defaultPlugins = [WheelGesturesPlugin({ forceWheelAxis: "x" })];
+
 type CarouselApi = UseEmblaCarouselType[1];
 type UseCarouselParameters = Parameters<typeof useEmblaCarousel>;
 type CarouselOptions = UseCarouselParameters[0];
@@ -55,7 +58,7 @@ function Carousel({
       ...opts,
       axis: orientation === "horizontal" ? "x" : "y",
     },
-    plugins,
+    plugins ?? defaultPlugins,
   );
   const [canScrollPrev, setCanScrollPrev] = React.useState(false);
   const [canScrollNext, setCanScrollNext] = React.useState(false);

hooks/use-search.ts

@@ -1,3 +1,4 @@
+import { useMemo } from "react";
 import useSWR from "swr";
 import { fetcher } from "@/lib/swr/fetcher";
 
@@ -26,8 +27,13 @@ export function useSearch(debouncedQuery: string) {
     },
   );
 
+  const results = useMemo(
+    () => data?.results?.slice(0, 8) ?? [],
+    [data?.results],
+  );
+
   return {
-    results: data?.results?.slice(0, 8) ?? [],
+    results,
     isLoading,
   };
 }

hooks/use-tilt-effect.ts

@@ -34,11 +34,17 @@ export function useTiltEffect(config: TiltConfig = {}) {
   const [disabled, setDisabled] = useState(false);
 
   useEffect(() => {
-    const mql = window.matchMedia("(prefers-reduced-motion: reduce)");
-    setDisabled(mql.matches);
-    const handler = (e: MediaQueryListEvent) => setDisabled(e.matches);
-    mql.addEventListener("change", handler);
-    return () => mql.removeEventListener("change", handler);
+    const reducedMotion = window.matchMedia("(prefers-reduced-motion: reduce)");
+    const finePointer = window.matchMedia("(pointer: fine)");
+    const update = () =>
+      setDisabled(reducedMotion.matches || !finePointer.matches);
+    update();
+    reducedMotion.addEventListener("change", update);
+    finePointer.addEventListener("change", update);
+    return () => {
+      reducedMotion.removeEventListener("change", update);
+      finePointer.removeEventListener("change", update);
+    };
   }, []);
 
   // Normalized mouse position [0,1], center = 0.5

hooks/use-time-ago.ts

@@ -1,5 +1,32 @@
 import { formatDistanceToNowStrict } from "date-fns";
-import { useEffect, useEffectEvent, useState } from "react";
+import { useSyncExternalStore } from "react";
+
+// Shared ticker — one interval regardless of how many components subscribe
+const TICK_MS = 30_000;
+let tick = Date.now();
+const listeners = new Set<() => void>();
+let timerId: ReturnType<typeof setInterval> | null = null;
+
+function subscribe(cb: () => void) {
+  if (listeners.size === 0) {
+    timerId = setInterval(() => {
+      tick = Date.now();
+      for (const l of listeners) l();
+    }, TICK_MS);
+  }
+  listeners.add(cb);
+  return () => {
+    listeners.delete(cb);
+    if (listeners.size === 0 && timerId) {
+      clearInterval(timerId);
+      timerId = null;
+    }
+  };
+}
+
+function getSnapshot() {
+  return tick;
+}
 
 function toTimestamp(date: string | Date | null | undefined): number | null {
   if (!date) return null;
@@ -9,26 +36,10 @@ function toTimestamp(date: string | Date | null | undefined): number | null {
 
 export function useTimeAgo(
   date: string | Date | null | undefined,
-  { intervalMs = 1_000, addSuffix = true, fallback = "" } = {},
+  { addSuffix = true, fallback = "" } = {},
 ): string {
+  useSyncExternalStore(subscribe, getSnapshot, getSnapshot);
   const ts = toTimestamp(date);
-
-  const [text, setText] = useState(() =>
-    ts === null ? fallback : formatDistanceToNowStrict(ts, { addSuffix }),
-  );
-
-  const tick = useEffectEvent(() => {
-    const next =
-      ts === null ? fallback : formatDistanceToNowStrict(ts, { addSuffix });
-    if (next !== text) setText(next);
-  });
-
-  useEffect(() => {
-    tick();
-    if (ts === null) return;
-    const id = setInterval(tick, intervalMs);
-    return () => clearInterval(id);
-  }, [ts, intervalMs]); // tick is NOT listed — that's the point
-
-  return text;
+  if (ts === null) return fallback;
+  return formatDistanceToNowStrict(ts, { addSuffix });
 }