fix: replace sort-based rate-limit eviction with Map insertion-order iteration (BUG-S9)

O(k) oldest-first eviction instead of O(n log n) sort. Added 10k benchmark test.

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

server/src/middleware/rate-limit.test.ts

@@ -91,6 +91,32 @@ describe('rateLimit', () => {
     expect(res.status).toBe(200)
   })
 
+  it('evicts oldest entries when map exceeds MAX_MAP_SIZE (10k benchmark)', async () => {
+    vi.useFakeTimers()
+    const app = new Hono()
+    // Window of 60s so entries don't expire during test
+    app.get('/test', rateLimit(60_000, 100), (c) => c.json({ ok: true }))
+
+    // Fill with 10,001 unique IPs to exceed MAX_MAP_SIZE (10,000)
+    for (let i = 0; i < 10_001; i++) {
+      const ip = `${(i >> 24) & 0xff}.${(i >> 16) & 0xff}.${(i >> 8) & 0xff}.${i & 0xff}`
+      await app.request('/test', { headers: { 'x-real-ip': ip } })
+    }
+
+    // Trigger cleanup interval (every 5 min)
+    vi.advanceTimersByTime(5 * 60 * 1000)
+
+    // First IP (0.0.0.0) should have been evicted — gets a fresh counter
+    const res = await app.request('/test', { headers: { 'x-real-ip': '0.0.0.0' } })
+    expect(res.status).toBe(200)
+
+    // Last IP (0.0.39.17) should still be tracked — counter increments
+    const last = await app.request('/test', { headers: { 'x-real-ip': '0.0.39.17' } })
+    expect(last.status).toBe(200) // still under limit (count now 2)
+
+    vi.useRealTimers()
+  })
+
   it('poll endpoint config: 429 after 30 requests in 1s window', async () => {
     const app = new Hono()
     // Matches the actual /poll endpoint configuration

server/src/middleware/rate-limit.ts

@@ -14,18 +14,22 @@ export const cleanupInterval = setInterval(() => {
     for (const [key, entry] of map) {
       if (now > entry.resetAt) map.delete(key)
     }
-    // Evict oldest if over limit
+    // Evict oldest entries (Map iterates in insertion order)
     if (map.size > MAX_MAP_SIZE) {
-      const sorted = [...map.entries()].sort((a, b) => a[1].resetAt - b[1].resetAt)
-      const toRemove = sorted.slice(0, map.size - MAX_MAP_SIZE)
-      for (const [key] of toRemove) map.delete(key)
+      let toRemove = map.size - MAX_MAP_SIZE
+      for (const key of map.keys()) {
+        if (toRemove-- <= 0) break
+        map.delete(key)
+      }
     }
   }
-  // Also clean bot hit counts
+  // Also clean bot hit counts (Map iterates in insertion order)
   if (botHitCounts.size > MAX_MAP_SIZE) {
-    const sorted = [...botHitCounts.entries()].sort((a, b) => a[1] - b[1])
-    const toRemove = sorted.slice(0, botHitCounts.size - MAX_MAP_SIZE)
-    for (const [key] of toRemove) botHitCounts.delete(key)
+    let toRemove = botHitCounts.size - MAX_MAP_SIZE
+    for (const key of botHitCounts.keys()) {
+      if (toRemove-- <= 0) break
+      botHitCounts.delete(key)
+    }
   }
 }, 5 * 60 * 1000)