diff --git a/frontend/src/api/types.ts b/frontend/src/api/types.ts
index e8b52ab..2970e5b 100644
--- a/frontend/src/api/types.ts
+++ b/frontend/src/api/types.ts
@@ -208,6 +208,7 @@ export interface QueryMetricRow {
   cache_hit_days: number
   db_query_days: number
   client_ip: string | null
+  client_id: string | null
 }
 
 export interface QueryMetricsPage {
@@ -252,7 +253,8 @@ export interface TimeSeriesBucket {
 }
 
 export interface TopClient {
-  client_ip: string
+  client: string
+  client_ip?: string
   query_count: number
   avg_elapsed_ms: number
 }
@@ -261,6 +263,7 @@ export interface QueryMetricsTimeSeries {
   buckets: TimeSeriesBucket[]
   topClients: TopClient[]
   granularity: 'HOURLY' | 'DAILY'
+  groupBy?: 'ip' | 'id'
 }
 
 export interface QueryMetricsParams {
diff --git a/frontend/src/pages/ApiMetrics.tsx b/frontend/src/pages/ApiMetrics.tsx
index 264ec8d..c3e95fc 100644
--- a/frontend/src/pages/ApiMetrics.tsx
+++ b/frontend/src/pages/ApiMetrics.tsx
@@ -136,6 +136,10 @@ export default function ApiMetrics() {
       key: 'client_ip', label: t('metrics.clientIp'), sortable: false,
       render: (row) => row.client_ip ? <span className="font-mono text-xs">{row.client_ip}</span> : '-',
     },
+    {
+      key: 'client_id', label: 'ID', sortable: false,
+      render: (row) => row.client_id ? <span className="font-mono text-xs">{row.client_id}</span> : '-',
+    },
   ]
 
   return (
diff --git a/frontend/src/pages/Dashboard.tsx b/frontend/src/pages/Dashboard.tsx
index 42db6a9..e2c6e06 100644
--- a/frontend/src/pages/Dashboard.tsx
+++ b/frontend/src/pages/Dashboard.tsx
@@ -326,30 +326,31 @@ export default function Dashboard() {
                 </div>
 
                 {/* Top Clients */}
-                {queryTs.topClients.length > 0 && (
-                  <div>
-                    <div className="mb-2 flex items-center gap-2">
-                      <span className="text-sm font-medium text-muted">{t('dashboard.topClients')}</span>
-                      <div className="flex overflow-hidden rounded-md border border-[var(--border-primary)] text-xs">
-                        <button
-                          type="button"
-                          className={`px-2 py-0.5 ${clientGroupBy === 'ip' ? 'bg-[var(--accent-primary)] text-white' : 'text-[var(--text-secondary)]'}`}
-                          onClick={() => setClientGroupBy('ip')}
-                        >IP</button>
-                        <button
-                          type="button"
-                          className={`px-2 py-0.5 ${clientGroupBy === 'id' ? 'bg-[var(--accent-primary)] text-white' : 'text-[var(--text-secondary)]'}`}
-                          onClick={() => setClientGroupBy('id')}
-                        >ID</button>
-                      </div>
+                <div>
+                  <div className="mb-2 flex items-center gap-2">
+                    <span className="text-sm font-medium text-muted">{t('dashboard.topClients')}</span>
+                    <div className="flex overflow-hidden rounded-md border border-[var(--border-primary)] text-xs">
+                      <button
+                        type="button"
+                        className={`px-2 py-0.5 transition-colors ${clientGroupBy === 'ip' ? 'bg-[var(--accent-primary)] text-white font-medium' : 'bg-[var(--bg-secondary)] text-[var(--text-secondary)] hover:bg-[var(--bg-hover)]'}`}
+                        onClick={() => setClientGroupBy('ip')}
+                      >IP</button>
+                      <button
+                        type="button"
+                        className={`px-2 py-0.5 transition-colors ${clientGroupBy === 'id' ? 'bg-[var(--accent-primary)] text-white font-medium' : 'bg-[var(--bg-secondary)] text-[var(--text-secondary)] hover:bg-[var(--bg-hover)]'}`}
+                        onClick={() => setClientGroupBy('id')}
+                      >ID</button>
                     </div>
+                  </div>
+                  {queryTs.topClients.length > 0 ? (
                     <div className="space-y-2">
                       {queryTs.topClients.map((c, i) => {
                         const maxCount = queryTs.topClients[0].query_count
                         const pct = maxCount > 0 ? (c.query_count / maxCount) * 100 : 0
+                        const label = c.client ?? c.client_ip ?? '-'
                         return (
-                          <div key={c.client_ip ?? i} className="flex items-center gap-3 text-sm">
-                            <span className="w-32 truncate font-mono text-xs">{c.client_ip ?? '-'}</span>
+                          <div key={label + i} className="flex items-center gap-3 text-sm">
+                            <span className="w-40 truncate font-mono text-xs" title={label}>{label}</span>
                             <div className="flex-1">
                               <div className="h-4 rounded bg-surface-hover">
                                 <div
@@ -365,8 +366,12 @@ export default function Dashboard() {
                         )
                       })}
                     </div>
-                  </div>
-                )}
+                  ) : (
+                    <div className="py-4 text-center text-xs text-muted">
+                      {clientGroupBy === 'id' ? '사용자 ID 데이터가 없습니다' : '클라이언트 데이터가 없습니다'}
+                    </div>
+                  )}
+                </div>
               </>
             ) : (
               <div className="py-8 text-center text-sm text-muted">{t('dashboard.noChartData')}</div>
diff --git a/src/main/java/gc/mda/signal_batch/monitoring/controller/QueryMetricsController.java b/src/main/java/gc/mda/signal_batch/monitoring/controller/QueryMetricsController.java
index 5afd5fc..eb18a0b 100644
--- a/src/main/java/gc/mda/signal_batch/monitoring/controller/QueryMetricsController.java
+++ b/src/main/java/gc/mda/signal_batch/monitoring/controller/QueryMetricsController.java
@@ -106,7 +106,7 @@ public class QueryMetricsController {
                        zoom_level, requested_mmsi, unique_vessels, total_tracks,
                        total_points, points_after_simplify, total_chunks,
                        response_bytes, elapsed_ms, db_query_ms, simplify_ms,
-                       cache_hit_days, db_query_days, client_ip
+                       cache_hit_days, db_query_days, client_ip, client_id
                 FROM signal.t_query_metrics
                 """ + whereClause +
                 " ORDER BY " + sortBy + " " + direction +