feat: implement API response caching with node-cache

- Add in-memory cache middleware with configurable TTL
- Cache GET endpoints: streets (5min), events (2min), posts (1min), rewards (10min)
- Automatic cache invalidation on POST/PUT/DELETE operations
- Add cache statistics endpoint (GET /api/cache/stats)
- Add cache management endpoint (DELETE /api/cache)
- Cache hit rate tracking and monitoring
- Pattern-based cache invalidation
- Optimized for Raspberry Pi deployment (lightweight in-memory)

🤖 Generated with Claude

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

backend/routes/cache.js

@@ -0,0 +1,43 @@
+const express = require("express");
+const auth = require("../middleware/auth");
+const { asyncHandler } = require("../middleware/errorHandler");
+const { getCacheStats, clearCache } = require("../middleware/cache");
+
+const router = express.Router();
+
+/**
+ * GET /api/cache/stats
+ * Get cache statistics
+ * @access Private (authenticated users)
+ */
+router.get(
+  "/stats",
+  auth,
+  asyncHandler(async (req, res) => {
+    const stats = getCacheStats();
+    res.json({
+      status: "operational",
+      ...stats,
+      timestamp: new Date().toISOString()
+    });
+  })
+);
+
+/**
+ * DELETE /api/cache
+ * Clear all cache
+ * @access Private (authenticated users - in production should be admin only)
+ */
+router.delete(
+  "/",
+  auth,
+  asyncHandler(async (req, res) => {
+    clearCache();
+    res.json({
+      msg: "Cache cleared successfully",
+      timestamp: new Date().toISOString()
+    });
+  })
+);
+
+module.exports = router;

backend/routes/events.js

@@ -9,6 +9,7 @@ const {
 } = require("../middleware/validators/eventValidator");
 const { paginate, buildPaginatedResponse } = require("../middleware/pagination");
 const couchdbService = require("../services/couchdbService");
+const { getCacheMiddleware, invalidateCacheByPattern } = require("../middleware/cache");
 
 const router = express.Router();
 
@@ -16,6 +17,7 @@ const router = express.Router();
 router.get(
   "/",
   paginate,
+  getCacheMiddleware(120), // Cache for 2 minutes
   asyncHandler(async (req, res) => {
     const { page, limit } = req.pagination;
 
@@ -50,6 +52,9 @@ router.post(
       location,
     });
 
+    // Invalidate events cache
+    invalidateCacheByPattern('/api/events');
+
     res.json(event);
   }),
 );

backend/routes/posts.js

@@ -10,6 +10,7 @@ const {
 const { upload, handleUploadError } = require("../middleware/upload");
 const { uploadImage, deleteImage } = require("../config/cloudinary");
 const { paginate, buildPaginatedResponse } = require("../middleware/pagination");
+const { getCacheMiddleware, invalidateCacheByPattern } = require("../middleware/cache");
 
 const router = express.Router();
 
@@ -17,6 +18,7 @@ const router = express.Router();
 router.get(
   "/",
   paginate,
+  getCacheMiddleware(60), // Cache for 1 minute
   asyncHandler(async (req, res) => {
     const { skip, limit, page } = req.pagination;
 
@@ -58,6 +60,9 @@ router.post(
 
     const post = await Post.create(postData);
 
+    // Invalidate posts cache
+    invalidateCacheByPattern('/api/posts');
+
     res.json({
       post,
       pointsAwarded: 5, // Standard post creation points

backend/routes/rewards.js

@@ -7,6 +7,7 @@ const {
   rewardIdValidation,
 } = require("../middleware/validators/rewardValidator");
 const { paginate, buildPaginatedResponse } = require("../middleware/pagination");
+const { getCacheMiddleware, invalidateCacheByPattern } = require("../middleware/cache");
 
 const router = express.Router();
 
@@ -14,6 +15,7 @@ const router = express.Router();
 router.get(
   "/",
   paginate,
+  getCacheMiddleware(600), // Cache for 10 minutes
   asyncHandler(async (req, res) => {
     const { page, limit } = req.pagination;
 
@@ -37,6 +39,9 @@ router.post(
       isPremium,
     });
 
+    // Invalidate rewards cache
+    invalidateCacheByPattern('/api/rewards');
+
     res.json(reward);
   }),
 );

backend/routes/streets.js

@@ -8,12 +8,14 @@ const {
   createStreetValidation,
   streetIdValidation,
 } = require("../middleware/validators/streetValidator");
+const { getCacheMiddleware, invalidateCacheByPattern } = require("../middleware/cache");
 
 const router = express.Router();
 
 // Get all streets (with pagination and filtering)
 router.get(
   "/",
+  getCacheMiddleware(300), // Cache for 5 minutes
   asyncHandler(async (req, res) => {
     const { buildPaginatedResponse } = require("../middleware/pagination");
 
@@ -81,6 +83,7 @@ router.get(
 router.get(
   "/:id",
   streetIdValidation,
+  getCacheMiddleware(300), // Cache for 5 minutes
   asyncHandler(async (req, res) => {
     const street = await Street.findById(req.params.id);
     if (!street) {
@@ -109,6 +112,9 @@ router.post(
       location,
     });
 
+    // Invalidate streets cache
+    invalidateCacheByPattern('/api/streets');
+
     res.json(street);
   }),
 );
@@ -156,6 +162,9 @@ router.put(
       user.stats.streetsAdopted = user.adoptedStreets.length;
       await user.save();
 
+      // Invalidate streets cache
+      invalidateCacheByPattern('/api/streets');
+
       // Award points for street adoption using CouchDB service
       const updatedUser = await couchdbService.updateUserPoints(
         req.user.id,