feat: add Redis caching for recipe queries with automatic invalidation

Implements Redis caching layer for recipe endpoints to reduce MongoDB load and improve response times:

- Install ioredis for Redis client with TypeScript support
- Create cache.ts with namespaced keys (homepage: prefix) to avoid conflicts with other Redis applications
- Add caching to recipe query endpoints (all_brief, by tag, in_season) with 1-hour TTL
- Implement automatic cache invalidation on recipe create/edit/delete operations
- Cache recipes before randomization to maximize cache reuse while maintaining random order per request
- Add graceful fallback to MongoDB if Redis is unavailable
- Update .env.example with Redis configuration (REDIS_HOST, REDIS_PORT)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/routes/api/rezepte/add/+server.ts

@@ -2,6 +2,7 @@ import type { RequestHandler } from '@sveltejs/kit';
 import { Recipe } from '../../../../models/Recipe';
 import { dbConnect } from '../../../../utils/db';
 import { error } from '@sveltejs/kit';
+import { invalidateRecipeCaches } from '$lib/server/cache';
 // header: use for bearer token for now
 // recipe json in body
 export const POST: RequestHandler = async ({request, cookies, locals}) => {
@@ -19,6 +20,8 @@ export const POST: RequestHandler = async ({request, cookies, locals}) => {
 	await dbConnect();
 	try{
       		await Recipe.create(recipe_json);
+		// Invalidate recipe caches after successful creation
+		await invalidateRecipeCaches();
 	} catch(e){
       		throw error(400, e)
       	}

src/routes/api/rezepte/delete/+server.ts

@@ -4,6 +4,7 @@ import { UserFavorites } from '../../../../models/UserFavorites';
 import { dbConnect } from '../../../../utils/db';
 import type {RecipeModelType} from '../../../../types/types';
 import { error } from '@sveltejs/kit';
+import { invalidateRecipeCaches } from '$lib/server/cache';
 // header: use for bearer token for now
 // recipe json in body
 export const POST: RequestHandler = async ({request, locals}) => {
@@ -69,6 +70,9 @@ export const POST: RequestHandler = async ({request, locals}) => {
 	// Delete the recipe
 	await Recipe.findOneAndDelete({short_name: short_name});
 
+	// Invalidate recipe caches after successful deletion
+	await invalidateRecipeCaches();
+
 	return new Response(JSON.stringify({msg: "Deleted recipe successfully"}),{
 		    status: 200,
   	});

src/routes/api/rezepte/edit/+server.ts

@@ -6,6 +6,7 @@ import { error } from '@sveltejs/kit';
 import { rename } from 'fs/promises';
 import { join } from 'path';
 import { existsSync } from 'fs';
+import { invalidateRecipeCaches } from '$lib/server/cache';
 
 // header: use for bearer token for now
 // recipe json in body
@@ -46,6 +47,10 @@ export const POST: RequestHandler = async ({request, locals}) => {
 	}
 
 	await Recipe.findOneAndUpdate({short_name: message.old_short_name }, recipe_json);
+
+	// Invalidate recipe caches after successful update
+	await invalidateRecipeCaches();
+
 	return new Response(JSON.stringify({msg: "Edited recipe successfully"}),{
 			    status: 200,
   	});

src/routes/api/rezepte/items/all_brief/+server.ts

@@ -3,9 +3,27 @@ import type { BriefRecipeType } from '../../../../../types/types';
 import { Recipe } from '../../../../../models/Recipe'
 import { dbConnect } from '../../../../../utils/db';
 import { rand_array } from '$lib/js/randomize';
+import cache from '$lib/server/cache';
 
 export const GET: RequestHandler = async ({params}) => {
-  await dbConnect();
-  let found_brief = rand_array(await Recipe.find({}, 'name short_name tags category icon description season dateModified').lean()) as BriefRecipeType[];
-  return json(JSON.parse(JSON.stringify(found_brief)));
+  const cacheKey = 'recipes:all_brief';
+
+  // Try cache first
+  let recipes: BriefRecipeType[] | null = null;
+  const cached = await cache.get(cacheKey);
+
+  if (cached) {
+    recipes = JSON.parse(cached);
+  } else {
+    // Cache miss - fetch from DB
+    await dbConnect();
+    recipes = await Recipe.find({}, 'name short_name tags category icon description season dateModified').lean() as BriefRecipeType[];
+
+    // Store in cache (1 hour TTL)
+    await cache.set(cacheKey, JSON.stringify(recipes), 3600);
+  }
+
+  // Apply randomization after fetching (so each request gets different order)
+  const randomized = rand_array(recipes);
+  return json(JSON.parse(JSON.stringify(randomized)));
 };

src/routes/api/rezepte/items/in_season/[month]/+server.ts

@@ -3,10 +3,27 @@ import { json, type RequestHandler } from '@sveltejs/kit';
 import { Recipe } from '../../../../../../models/Recipe'
 import { dbConnect } from '../../../../../../utils/db';
 import { rand_array } from '$lib/js/randomize';
+import cache from '$lib/server/cache';
 
 export const GET: RequestHandler = async ({params}) => {
-  await dbConnect();
-  let found_in_season = rand_array(await Recipe.find({season: params.month, icon: {$ne: "🍽️"}}, 'name short_name images tags category icon description season dateModified').lean());
-  found_in_season = JSON.parse(JSON.stringify(found_in_season));
-  return json(found_in_season);
+  const cacheKey = `recipes:in_season:${params.month}`;
+
+  // Try cache first
+  let recipes = null;
+  const cached = await cache.get(cacheKey);
+
+  if (cached) {
+    recipes = JSON.parse(cached);
+  } else {
+    // Cache miss - fetch from DB
+    await dbConnect();
+    recipes = await Recipe.find({season: params.month, icon: {$ne: "🍽️"}}, 'name short_name images tags category icon description season dateModified').lean();
+
+    // Store in cache (1 hour TTL)
+    await cache.set(cacheKey, JSON.stringify(recipes), 3600);
+  }
+
+  // Apply randomization after fetching (so each request gets different order)
+  const randomized = rand_array(recipes);
+  return json(JSON.parse(JSON.stringify(randomized)));
 };

src/routes/api/rezepte/items/tag/[tag]/+server.ts

@@ -3,11 +3,27 @@ import { Recipe } from '../../../../../../models/Recipe';
 import { dbConnect } from '../../../../../../utils/db';
 import type {BriefRecipeType} from '../../../../../../types/types';
 import { rand_array } from '$lib/js/randomize';
+import cache from '$lib/server/cache';
 
 export const GET: RequestHandler = async ({params}) => {
-  await dbConnect();
-  let recipes = rand_array(await Recipe.find({tags: params.tag}, 'name short_name images tags category icon description season dateModified').lean()) as BriefRecipeType[];
+  const cacheKey = `recipes:tag:${params.tag}`;
 
-  recipes = JSON.parse(JSON.stringify(recipes));
-  return json(recipes);
+  // Try cache first
+  let recipes: BriefRecipeType[] | null = null;
+  const cached = await cache.get(cacheKey);
+
+  if (cached) {
+    recipes = JSON.parse(cached);
+  } else {
+    // Cache miss - fetch from DB
+    await dbConnect();
+    recipes = await Recipe.find({tags: params.tag}, 'name short_name images tags category icon description season dateModified').lean() as BriefRecipeType[];
+
+    // Store in cache (1 hour TTL)
+    await cache.set(cacheKey, JSON.stringify(recipes), 3600);
+  }
+
+  // Apply randomization after fetching (so each request gets different order)
+  const randomized = rand_array(recipes);
+  return json(JSON.parse(JSON.stringify(randomized)));
 };