diff --git a/src/server/routes/mileage/cache.ts b/src/server/routes/mileage/cache.ts
new file mode 100644
index 0000000..e22ec20
--- /dev/null
+++ b/src/server/routes/mileage/cache.ts
@@ -0,0 +1,179 @@
+import pool from '../../db.js';
+import mileagePool from '../../mileage-db.js';
+import { fetchVehicleInfoMap } from './vehicle-info.js';
+import type { CachedVehicle, MonitoringCache, MonitoringFilters, PlatePrefix, VehicleInfoRow } from './types.js';
+
+let monitoringCache: MonitoringCache | null = null;
+
+export function getCache(): MonitoringCache | null {
+  return monitoringCache;
+}
+
+const DEPT_ORDER = ['一', '二', '三', '四', '五', '六', '七', '八', '九', '十'];
+
+function sortDepartments(departments: string[]): string[] {
+  return departments.sort((a, b) => {
+    const ai = DEPT_ORDER.findIndex(d => a.includes(d));
+    const bi = DEPT_ORDER.findIndex(d => b.includes(d));
+    return (ai === -1 ? 99 : ai) - (bi === -1 ? 99 : bi);
+  });
+}
+
+function buildFilters(vehicles: CachedVehicle[], targetNames: string[]): MonitoringFilters {
+  const departments = sortDepartments(
+    Array.from(new Set(vehicles.map(v => v.department).filter((d): d is string => d !== null)))
+  );
+  const customers = Array.from(new Set(vehicles.map(v => v.customer).filter((c): c is string => c !== null)));
+  const plates = vehicles.map(v => v.plate);
+  const projects = Array.from(new Set(vehicles.map(v => v.project).filter((p): p is string => p !== null)));
+  const entities = Array.from(new Set(vehicles.map(v => v.entity).filter((e): e is string => e !== null)));
+  const rentStatuses = Array.from(new Set(vehicles.map(v => v.rentStatus).filter((r): r is string => r !== null)));
+
+  const prefixCount = new Map<string, number>();
+  for (const v of vehicles) {
+    const p = v.plate.charAt(0);
+    prefixCount.set(p, (prefixCount.get(p) || 0) + 1);
+  }
+  const platePrefixes: PlatePrefix[] = Array.from(prefixCount.entries())
+    .map(([prefix, count]) => ({ prefix, count }))
+    .sort((a, b) => b.count - a.count);
+
+  return { departments, customers, plates, projects, entities, rentStatuses, platePrefixes, targetNames };
+}
+
+interface MileageRow {
+  plate: string;
+  vin: string;
+  daily_km: string;
+  total_km: string | null;
+  source: string;
+}
+
+function mergeVehicles(
+  mileageRows: MileageRow[],
+  infoMap: Map<string, VehicleInfoRow>,
+  yesterdayMap: Map<string, number>,
+): CachedVehicle[] {
+  const mileageMap = new Map<string, MileageRow>();
+  for (const row of mileageRows) {
+    const existing = mileageMap.get(row.plate);
+    if (!existing || Number(row.daily_km) > Number(existing.daily_km)) {
+      mileageMap.set(row.plate, row);
+    }
+  }
+
+  return Array.from(mileageMap.values()).map(m => {
+    const info = infoMap.get(m.plate);
+    const dailyKm = Number(m.daily_km) || 0;
+    const source = m.source || 'NONE';
+    return {
+      plate: m.plate,
+      vin: m.vin,
+      dailyKm,
+      totalKm: m.total_km !== null ? Number(m.total_km) : null,
+      source,
+      isOnline: source !== 'NONE' && dailyKm > 0,
+      isDataSynced: source !== 'NONE',
+      customer: info?.customer || null,
+      department: info?.department || null,
+      manager: info?.manager || null,
+      rentStatus: info?.rent_status || null,
+      entity: info?.entity || null,
+      project: info?.project || null,
+      yesterdayKm: yesterdayMap.get(m.plate) || 0,
+    };
+  });
+}
+
+export async function refreshMonitoringCache(): Promise<void> {
+  try {
+    console.log('[mileage] refreshing monitoring cache...');
+    const start = Date.now();
+
+    const [mileageRows, yesterdayMap, infoMap, targetRows] = await Promise.all([
+      (async () => {
+        const [dateRows] = await mileagePool.execute(
+          'SELECT MAX(stat_date) as latest FROM v_vehicle_daily_stats'
+        ) as [{ latest: string | null }[], unknown];
+        const latestDate = dateRows[0]?.latest;
+        if (!latestDate) return [];
+        const [rows] = await mileagePool.execute(
+          'SELECT plate, vin, daily_km, total_km, source FROM v_vehicle_daily_stats WHERE stat_date = ?',
+          [latestDate]
+        ) as [MileageRow[], unknown];
+        return rows;
+      })(),
+      (async () => {
+        const [rows] = await mileagePool.execute(
+          `SELECT plate, daily_km FROM v_vehicle_daily_stats
+           WHERE stat_date = DATE_SUB((SELECT MAX(stat_date) FROM v_vehicle_daily_stats), INTERVAL 1 DAY)`
+        ) as [{ plate: string; daily_km: string }[], unknown];
+        const map = new Map<string, number>();
+        for (const r of rows) {
+          const km = Number(r.daily_km) || 0;
+          const existing = map.get(r.plate) || 0;
+          if (km > existing) map.set(r.plate, km);
+        }
+        return map;
+      })(),
+      fetchVehicleInfoMap(),
+      pool.execute(
+        `SELECT t.id, t.target_name, v.plate_number
+         FROM tab_mileage_assessment_target t
+         JOIN tab_mileage_assessment_vehicle v ON v.target_id = t.id AND v.is_deleted = 0
+         WHERE t.is_deleted = 0`
+      ).then(([rows]) => rows as { id: number; target_name: string; plate_number: string }[]),
+    ]);
+
+    const targetPlatesMap = new Map<string, Set<string>>();
+    for (const r of targetRows) {
+      const set = targetPlatesMap.get(r.target_name) || new Set();
+      set.add(r.plate_number);
+      targetPlatesMap.set(r.target_name, set);
+    }
+    const targetNames = Array.from(targetPlatesMap.keys());
+
+    const vehicles = mergeVehicles(mileageRows, infoMap, yesterdayMap);
+    const totalToday = vehicles.reduce((sum, v) => sum + v.dailyKm, 0);
+    const totalAll = vehicles.reduce((sum, v) => sum + (v.totalKm || 0), 0);
+
+    monitoringCache = {
+      vehicles,
+      stats: { totalToday, totalAll, vehicleCount: vehicles.length },
+      filters: buildFilters(vehicles, targetNames),
+      targetPlatesMap,
+      updatedAt: new Date().toISOString(),
+    };
+
+    console.log(`[mileage] cache refreshed: ${vehicles.length} vehicles in ${Date.now() - start}ms`);
+  } catch (e: unknown) {
+    console.error('[mileage] cache refresh error:', e);
+  }
+}
+
+export async function queryDateMileage(dateStr: string): Promise<CachedVehicle[]> {
+  const [mileageRows, yesterdayRows, infoMap] = await Promise.all([
+    mileagePool.execute(
+      'SELECT plate, vin, daily_km, total_km, source FROM v_vehicle_daily_stats WHERE stat_date = ?',
+      [dateStr]
+    ).then(([r]) => r as MileageRow[]),
+    mileagePool.execute(
+      'SELECT plate, daily_km FROM v_vehicle_daily_stats WHERE stat_date = DATE_SUB(?, INTERVAL 1 DAY)',
+      [dateStr]
+    ).then(([r]) => r as { plate: string; daily_km: string }[]),
+    fetchVehicleInfoMap(),
+  ]);
+
+  const yesterdayMap = new Map<string, number>();
+  for (const r of yesterdayRows) {
+    const km = Number(r.daily_km) || 0;
+    const existing = yesterdayMap.get(r.plate) || 0;
+    if (km > existing) yesterdayMap.set(r.plate, km);
+  }
+
+  return mergeVehicles(mileageRows, infoMap, yesterdayMap);
+}
+
+export function buildDateFilters(vehicles: CachedVehicle[]): MonitoringFilters {
+  return buildFilters(vehicles, monitoringCache?.filters.targetNames || []);
+}