diff --git a/.jules/bolt.md b/.jules/bolt.md
index 9b7817f..edc00d2 100644
--- a/.jules/bolt.md
+++ b/.jules/bolt.md
@@ -14,3 +14,7 @@
 ## 2026-04-24 - [OOM prevention through promise chunking]
 **Learning:** When fetching unbounded large collections (like photo albums and their assets), using concurrent `Promise.all` over the entire array can cause Node.js Out of Memory (OOM) crashes.
 **Action:** Instead of `Promise.all(array.map(...))`, use a chunked data fetching approach (e.g., `Promise.all` within a `for` loop processing chunks of e.g. 10 items) to balance memory constraints with concurrent network speed.
+
+## 2024-05-30 - [O(1) Memory Bucketing for Coordinate Aggregation]
+**Learning:** When bucketing or grouping large datasets (e.g., thousands of map coordinates into geographical clusters), array allocations (`[].push()`) followed by `reduce` operations create an O(N) memory overhead per bucket and expensive post-processing loops.
+**Action:** Replace memory-heavy array collections with running statistical accumulators (e.g., `latSum`, `lngSum`, `count`) directly on the bucket. This reduces bucket memory from O(N) to O(1).
diff --git a/lib/mapService.ts b/lib/mapService.ts
index 7e2d176..0d062c5 100644
--- a/lib/mapService.ts
+++ b/lib/mapService.ts
@@ -17,77 +17,101 @@ export interface MapLocation {
  * Aggregate all geotagged photos into location-level markers.
  * Returns one entry per unique city+country with averaged lat/lng.
  */
+let pendingMapDataPromise: Promise<MapLocation[]> | null = null;
+
 export async function getMapData(): Promise<MapLocation[]> {
   const config = getConfig();
   const cacheKey = 'map-data';
   const cached = cache.get<MapLocation[]>(cacheKey);
   if (cached) return cached;
 
-  const albums = await immich.getAlbums();
+  if (pendingMapDataPromise) return pendingMapDataPromise;
 
-  // Build a lookup: album ID → { name, slug, subpageSlug? }
-  const albumMeta = new Map<string, { name: string; slug: string; subpageSlug?: string }>();
-  for (const a of albums) {
-    // Check if this album belongs to a subpage
-    const sp = config.subpages.find((s) => s.albumIds.includes(a.id));
-    albumMeta.set(a.id, { name: a.albumName, slug: a.slug, subpageSlug: sp?.slug });
-  }
+  pendingMapDataPromise = (async () => {
+    try {
+      const albums = await immich.getAlbums();
 
-  // Fetch full album data (with assets) for each
-  // Process in chunks of 10 to balance network speed and prevent Out of Memory (OOM)
-  // crashes from fetching thousands of assets simultaneously.
-  const fullAlbums: (Awaited<ReturnType<typeof immich.getAlbum>> | null)[] = [];
-  const chunkSize = 10;
-  for (let i = 0; i < albums.length; i += chunkSize) {
-    const chunk = albums.slice(i, i + chunkSize);
-    const chunkResults = await Promise.all(chunk.map((a) => immich.getAlbum(a.id)));
-    fullAlbums.push(...chunkResults);
-  }
-
-  // Bucket assets by city+country
-  const buckets = new Map<
-    string,
-    { lats: number[]; lngs: number[]; count: number; coverAssetId: string; albumIds: Set<string> }
-  >();
-
-  for (const album of fullAlbums) {
-    if (!album) continue;
-    for (const asset of album.assets) {
-      const exif = asset.exifInfo;
-      if (!exif?.latitude || !exif?.longitude || !exif?.city || !exif?.country) continue;
-
-      const key = `${exif.city}|${exif.country}`;
-      let bucket = buckets.get(key);
-      if (!bucket) {
-        bucket = { lats: [], lngs: [], count: 0, coverAssetId: asset.id, albumIds: new Set() };
-        buckets.set(key, bucket);
+      // Build a lookup: album ID → { name, slug, subpageSlug? }
+      const albumMeta = new Map<string, { name: string; slug: string; subpageSlug?: string }>();
+      for (const a of albums) {
+        // Check if this album belongs to a subpage
+        const sp = config.subpages.find((s) => s.albumIds.includes(a.id));
+        albumMeta.set(a.id, { name: a.albumName, slug: a.slug, subpageSlug: sp?.slug });
       }
-      bucket.lats.push(exif.latitude);
-      bucket.lngs.push(exif.longitude);
-      bucket.count++;
-      bucket.albumIds.add(album.id);
+
+      // Fetch full album data (with assets) for each
+      // Process in chunks of 10 to balance network speed and prevent Out of Memory (OOM)
+      // crashes from fetching thousands of assets simultaneously.
+      const fullAlbums: (Awaited<ReturnType<typeof immich.getAlbum>> | null)[] = [];
+      const chunkSize = 10;
+      for (let i = 0; i < albums.length; i += chunkSize) {
+        const chunk = albums.slice(i, i + chunkSize);
+        const chunkResults = await Promise.all(chunk.map((a) => immich.getAlbum(a.id)));
+        fullAlbums.push(...chunkResults);
+      }
+
+      // Bucket assets by city+country
+      const buckets = new Map<
+        string,
+        {
+          latSum: number;
+          lngSum: number;
+          count: number;
+          coverAssetId: string;
+          albumIds: Set<string>;
+        }
+      >();
+
+      for (const album of fullAlbums) {
+        if (!album) continue;
+        for (const asset of album.assets) {
+          const exif = asset.exifInfo;
+          if (!exif?.latitude || !exif?.longitude || !exif?.city || !exif?.country) continue;
+
+          const key = `${exif.city}|${exif.country}`;
+          let bucket = buckets.get(key);
+          if (!bucket) {
+            bucket = {
+              latSum: 0,
+              lngSum: 0,
+              count: 0,
+              coverAssetId: asset.id,
+              albumIds: new Set(),
+            };
+            buckets.set(key, bucket);
+          }
+          bucket.latSum += exif.latitude;
+          bucket.lngSum += exif.longitude;
+          bucket.count++;
+          bucket.albumIds.add(album.id);
+        }
+      }
+
+      // Convert buckets to MapLocation[]
+      const locations: MapLocation[] = [];
+      for (const [key, bucket] of buckets) {
+        const [city, country] = key.split('|');
+        const lat = bucket.latSum / bucket.count;
+        const lng = bucket.lngSum / bucket.count;
+        locations.push({
+          city,
+          country,
+          lat,
+          lng,
+          photoCount: bucket.count,
+          coverAssetId: bucket.coverAssetId,
+          albums: [...bucket.albumIds]
+            .map((id) => albumMeta.get(id))
+            .filter((m): m is NonNullable<typeof m> => !!m),
+        });
+      }
+
+      cache.set(cacheKey, locations, config.cacheTtl);
+      return locations;
+    } finally {
+      pendingMapDataPromise = null;
     }
-  }
+  })();
 
-  // Convert buckets to MapLocation[]
-  const locations: MapLocation[] = [];
-  for (const [key, bucket] of buckets) {
-    const [city, country] = key.split('|');
-    const lat = bucket.lats.reduce((a, b) => a + b, 0) / bucket.lats.length;
-    const lng = bucket.lngs.reduce((a, b) => a + b, 0) / bucket.lngs.length;
-    locations.push({
-      city,
-      country,
-      lat,
-      lng,
-      photoCount: bucket.count,
-      coverAssetId: bucket.coverAssetId,
-      albums: [...bucket.albumIds]
-        .map((id) => albumMeta.get(id))
-        .filter((m): m is NonNullable<typeof m> => !!m),
-    });
-  }
-
-  cache.set(cacheKey, locations, config.cacheTtl);
-  return locations;
+  return pendingMapDataPromise;
 }