diff --git a/loadtests/backend/performance_v0124.js b/loadtests/backend/performance_v0124.js
new file mode 100644
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+++ b/loadtests/backend/performance_v0124.js
@@ -0,0 +1,192 @@
+/**
+ * v0.12.4 Performance & Scalability Load Test
+ * Reference: ORIGIN_PERFORMANCE_TARGETS.md §8.4
+ *
+ * Scenarios:
+ *   - smoke: 10 VUs, 1 min (sanity check)
+ *   - load:  500 VUs, 5 min (normal traffic)
+ *   - stress: 1000 VUs, 3 min (peak load)
+ *
+ * Usage:
+ *   k6 run loadtests/backend/performance_v0124.js
+ *   k6 run --env SCENARIO=smoke loadtests/backend/performance_v0124.js
+ *   k6 run --env SCENARIO=stress loadtests/backend/performance_v0124.js
+ */
+import http from 'k6/http';
+import { check, sleep, group } from 'k6';
+import { Rate, Counter, Trend } from 'k6/metrics';
+
+// Custom metrics
+const errorRate = new Rate('error_rate');
+const cacheHits = new Counter('cache_hits');
+const cacheMisses = new Counter('cache_misses');
+const apiDuration = new Trend('api_duration', true);
+
+const BASE_URL = __ENV.BASE_URL || __ENV.API_ORIGIN || 'http://localhost:8080';
+const AUTH_TOKEN = __ENV.AUTH_TOKEN || '';
+const SCENARIO = __ENV.SCENARIO || 'load';
+
+// Scenario configurations
+const scenarios = {
+  smoke: {
+    stages: [
+      { duration: '15s', target: 5 },
+      { duration: '30s', target: 10 },
+      { duration: '15s', target: 0 },
+    ],
+  },
+  load: {
+    stages: [
+      { duration: '30s', target: 50 },
+      { duration: '1m', target: 200 },
+      { duration: '2m', target: 500 },
+      { duration: '1m', target: 200 },
+      { duration: '30s', target: 0 },
+    ],
+  },
+  stress: {
+    stages: [
+      { duration: '30s', target: 100 },
+      { duration: '1m', target: 500 },
+      { duration: '1m', target: 1000 },
+      { duration: '30s', target: 1000 },
+      { duration: '30s', target: 0 },
+    ],
+  },
+};
+
+export const options = {
+  stages: scenarios[SCENARIO]?.stages || scenarios.load.stages,
+  thresholds: {
+    // p95 < 100ms for main API endpoints
+    http_req_duration: ['p(95)<100', 'p(99)<200'],
+    // Error rate < 1%
+    error_rate: ['rate<0.01'],
+    // Custom API duration
+    api_duration: ['p(95)<100', 'p(99)<200'],
+  },
+  // Graceful stop
+  gracefulStop: '10s',
+};
+
+function headers() {
+  const h = { 'Content-Type': 'application/json' };
+  if (AUTH_TOKEN) {
+    h['Authorization'] = `Bearer ${AUTH_TOKEN}`;
+  }
+  return h;
+}
+
+export default function () {
+  const h = headers();
+
+  // Health check (should always be fast)
+  group('health', () => {
+    const res = http.get(`${BASE_URL}/health`, { headers: h });
+    check(res, { 'health 200': (r) => r.status === 200 });
+    errorRate.add(res.status >= 500);
+  });
+
+  // Track listing (most frequent endpoint)
+  group('tracks_list', () => {
+    const res = http.get(`${BASE_URL}/api/v1/tracks?page=1&limit=20`, {
+      headers: h,
+    });
+    check(res, {
+      'tracks list 2xx or 401': (r) => (r.status >= 200 && r.status < 300) || r.status === 401,
+    });
+    errorRate.add(res.status >= 500);
+    apiDuration.add(res.timings.duration);
+
+    // Check cache header
+    if (res.headers['X-Cache'] === 'HIT') {
+      cacheHits.add(1);
+    } else {
+      cacheMisses.add(1);
+    }
+  });
+  sleep(0.3);
+
+  // Search endpoint
+  group('search', () => {
+    const queries = ['rock', 'jazz', 'piano', 'guitar', 'beat'];
+    const q = queries[Math.floor(Math.random() * queries.length)];
+    const res = http.get(`${BASE_URL}/api/v1/search?q=${q}&limit=10`, {
+      headers: h,
+    });
+    check(res, {
+      'search 2xx or 401': (r) => (r.status >= 200 && r.status < 300) || r.status === 401,
+    });
+    errorRate.add(res.status >= 500);
+    apiDuration.add(res.timings.duration);
+  });
+  sleep(0.3);
+
+  // Track detail (if tracks available)
+  group('track_detail', () => {
+    const listRes = http.get(`${BASE_URL}/api/v1/tracks?page=1&limit=5`, {
+      headers: h,
+    });
+    if (listRes.status === 200) {
+      try {
+        const body = JSON.parse(listRes.body);
+        const tracks = body.data?.tracks || body.data || body.tracks || [];
+        if (Array.isArray(tracks) && tracks.length > 0) {
+          const trackId = tracks[0].id || tracks[0].ID;
+          if (trackId) {
+            const detailRes = http.get(
+              `${BASE_URL}/api/v1/tracks/${trackId}`,
+              { headers: h }
+            );
+            check(detailRes, {
+              'track detail 2xx or 404': (r) =>
+                (r.status >= 200 && r.status < 300) || r.status === 404,
+            });
+            errorRate.add(detailRes.status >= 500);
+            apiDuration.add(detailRes.timings.duration);
+          }
+        }
+      } catch (_e) {
+        // Parse error — skip
+      }
+    }
+  });
+  sleep(0.3);
+
+  // User profile endpoint
+  group('user_profiles', () => {
+    const res = http.get(`${BASE_URL}/api/v1/users?page=1&limit=10`, {
+      headers: h,
+    });
+    check(res, {
+      'users list 2xx or 401': (r) => (r.status >= 200 && r.status < 300) || r.status === 401,
+    });
+    errorRate.add(res.status >= 500);
+    apiDuration.add(res.timings.duration);
+  });
+  sleep(0.5);
+}
+
+export function handleSummary(data) {
+  const p95 = data.metrics.http_req_duration?.values?.['p(95)'] || 'N/A';
+  const p99 = data.metrics.http_req_duration?.values?.['p(99)'] || 'N/A';
+  const errRate = data.metrics.error_rate?.values?.rate || 0;
+  const hits = data.metrics.cache_hits?.values?.count || 0;
+  const misses = data.metrics.cache_misses?.values?.count || 0;
+  const hitRatio = hits + misses > 0 ? ((hits / (hits + misses)) * 100).toFixed(1) : '0';
+
+  console.log(`
+═══════════════════════════════════════════
+  v0.12.4 Performance Test Results (${SCENARIO})
+═══════════════════════════════════════════
+  p95 latency:    ${typeof p95 === 'number' ? p95.toFixed(2) : p95}ms (target: <100ms)
+  p99 latency:    ${typeof p99 === 'number' ? p99.toFixed(2) : p99}ms (target: <200ms)
+  Error rate:     ${(errRate * 100).toFixed(2)}% (target: <1%)
+  Cache hit ratio: ${hitRatio}% (target: >90%)
+  Cache hits:     ${hits}
+  Cache misses:   ${misses}
+═══════════════════════════════════════════
+  `);
+
+  return {};
+}