diff --git a/services/platform-service/src/modules/telemetry/routes.ts b/services/platform-service/src/modules/telemetry/routes.ts
index b68546b6..7657c758 100644
--- a/services/platform-service/src/modules/telemetry/routes.ts
+++ b/services/platform-service/src/modules/telemetry/routes.ts
@@ -39,6 +39,35 @@ const PII_SCAN_ENABLED = process.env.TELEMETRY_PII_SCAN_ENABLED !== 'false';
 const CLIENT_BATCH_SIZE = parseInt(process.env.TELEMETRY_CLIENT_BATCH_SIZE ?? '20', 10);
 const CLIENT_FLUSH_MS = parseInt(process.env.TELEMETRY_CLIENT_FLUSH_MS ?? '60000', 10);
 const CLIENT_MAX_QUEUE = parseInt(process.env.TELEMETRY_CLIENT_MAX_QUEUE ?? '200', 10);
+const RATE_LIMIT_PER_MIN = parseInt(process.env.TELEMETRY_RATE_LIMIT_PER_MIN ?? '100', 10);
+const RATE_LIMIT_WINDOW_MS = 60_000;
+
+// ─── Rate limiter (in-memory sliding window per installId) ──────
+
+const rateBuckets = new Map<string, { count: number; windowStart: number }>();
+
+export function checkRateLimit(installId: string, eventCount: number): boolean {
+  const now = Date.now();
+  const bucket = rateBuckets.get(installId);
+  if (!bucket || now - bucket.windowStart > RATE_LIMIT_WINDOW_MS) {
+    rateBuckets.set(installId, { count: eventCount, windowStart: now });
+    return true;
+  }
+  if (bucket.count + eventCount > RATE_LIMIT_PER_MIN) {
+    return false;
+  }
+  bucket.count += eventCount;
+  return true;
+}
+
+// Periodic cleanup of stale rate-limit buckets (every 5 min)
+const _cleanupTimer = globalThis.setInterval(() => {
+  const cutoff = Date.now() - RATE_LIMIT_WINDOW_MS * 2;
+  for (const [key, bucket] of rateBuckets) {
+    if (bucket.windowStart < cutoff) rateBuckets.delete(key);
+  }
+}, 300_000);
+if (typeof _cleanupTimer === 'object' && 'unref' in _cleanupTimer) _cleanupTimer.unref();
 
 /** PII patterns — reject events containing these. */
 const PII_PATTERNS = [
@@ -334,16 +363,36 @@ export async function telemetryRoutes(app: FastifyInstance) {
     }
 
     const { productId, events } = parsed.data;
+
+    // Rate limiting per installId
+    const rateLimitKey = installToken || req.jwtPayload?.sub || 'unknown';
+    if (!checkRateLimit(rateLimitKey, events.length)) {
+      reply.code(429);
+      return {
+        accepted: 0,
+        rejected: events.length,
+        errors: [{ index: 0, reason: `Rate limit exceeded (${RATE_LIMIT_PER_MIN} events/min)` }],
+        serverTime: new Date().toISOString(),
+      };
+    }
+
+    // Batch deduplication by event.id
+    const seenIds = new Set<string>();
+    const dedupedEvents = events.filter(e => {
+      if (seenIds.has(e.id)) return false;
+      seenIds.add(e.id);
+      return true;
+    });
     const now = new Date().toISOString();
     const ttl = DEFAULT_EVENT_TTL_DAYS * 86400;
 
     let accepted = 0;
-    let rejected = 0;
+    let rejected = events.length - dedupedEvents.length; // duplicates
     const errors: Array<{ index: number; reason: string }> = [];
     const docsToInsert: TelemetryEventDoc[] = [];
 
-    for (let i = 0; i < events.length; i++) {
-      const event = events[i];
+    for (let i = 0; i < dedupedEvents.length; i++) {
+      const event = dedupedEvents[i];
 
       // Validate productId matches request-level
       if (event.productId !== productId) {
@@ -395,8 +444,8 @@ export async function telemetryRoutes(app: FastifyInstance) {
     };
   });
 
-  // ── Collection config (client poll) ───────────────────────────
-  app.get('/telemetry/config', async req => {
+  // ── Collection config (client poll) with ETag caching ─────────
+  app.get('/telemetry/config', async (req, reply) => {
     if (!TELEMETRY_ENABLED) {
       return {
         enabled: false,
@@ -415,7 +464,19 @@ export async function telemetryRoutes(app: FastifyInstance) {
     const allPolicies = await repo.listPolicies(productId);
     const activePolicies = allPolicies.filter(p => p.enabled && policyMatchesContext(p, ctx));
 
-    return mergePolicies(activePolicies);
+    const config = mergePolicies(activePolicies);
+
+    // ETag caching: hash the config to avoid redundant client processing
+    const etag = createHash('sha256').update(JSON.stringify(config)).digest('hex').substring(0, 16);
+    const clientEtag = req.headers['if-none-match'];
+    if (clientEtag === `"${etag}"`) {
+      reply.code(304);
+      return;
+    }
+
+    reply.header('ETag', `"${etag}"`);
+    reply.header('Cache-Control', 'private, max-age=60');
+    return config;
   });
 
   // ── Admin: query events ───────────────────────────────────────
diff --git a/services/platform-service/src/modules/telemetry/telemetry.test.ts b/services/platform-service/src/modules/telemetry/telemetry.test.ts
index 18c625fd..3a6787c1 100644
--- a/services/platform-service/src/modules/telemetry/telemetry.test.ts
+++ b/services/platform-service/src/modules/telemetry/telemetry.test.ts
@@ -19,6 +19,7 @@ import {
   generateFingerprint,
   policyMatchesContext,
   mergePolicies,
+  checkRateLimit,
 } from './routes.js';
 
 // ─── Minimal valid event for reuse ──────────────────────────────────
@@ -648,3 +649,27 @@ describe('mergePolicies', () => {
     expect(config.modules.length).toBe(2);
   });
 });
+
+// ─── checkRateLimit ─────────────────────────────────────────────
+
+describe('checkRateLimit', () => {
+  it('allows events within the limit', () => {
+    const id = `test_rate_${Date.now()}`;
+    expect(checkRateLimit(id, 50)).toBe(true);
+    expect(checkRateLimit(id, 49)).toBe(true);
+  });
+
+  it('rejects events that exceed the limit', () => {
+    const id = `test_rate_exceed_${Date.now()}`;
+    expect(checkRateLimit(id, 80)).toBe(true);
+    expect(checkRateLimit(id, 30)).toBe(false); // 80 + 30 > 100
+  });
+
+  it('different installIds have separate buckets', () => {
+    const id1 = `test_rate_a_${Date.now()}`;
+    const id2 = `test_rate_b_${Date.now()}`;
+    expect(checkRateLimit(id1, 90)).toBe(true);
+    expect(checkRateLimit(id2, 90)).toBe(true); // separate bucket
+    expect(checkRateLimit(id1, 20)).toBe(false); // id1 exceeded
+  });
+});