diff --git a/ext/wasm/api/sqlite3-vfs-kvvfs.c-pp.js b/ext/wasm/api/sqlite3-vfs-kvvfs.c-pp.js
index a78c0548b7..f04ae379a0 100644
--- a/ext/wasm/api/sqlite3-vfs-kvvfs.c-pp.js
+++ b/ext/wasm/api/sqlite3-vfs-kvvfs.c-pp.js
@@ -209,17 +209,21 @@ globalThis.sqlite3ApiBootstrap.initializers.push(function(sqlite3){
      and recreating it whenever a property index might be invalidated.
   */
   class KVVfsStorage {
-    #map;
-    #keys;
-    #getKeys(){return this.#keys ??= Object.keys(this.#map);}
+    #map = Object.create(null);
+    #keys = null;
+    #size = 0;
 
     constructor(){
       this.clear();
     }
 
+    #getKeys(){
+      return this.#keys ??= Object.keys(this.#map);
+    }
+
     key(n){
       const k = this.#getKeys();
-      return n<k.length ? k[n] : null;
+      return (n>=0 && n<k.length) ? k[n] : null;
     }
 
     getItem(k){
@@ -227,14 +231,17 @@ globalThis.sqlite3ApiBootstrap.initializers.push(function(sqlite3){
     }
 
     setItem(k,v){
-      if( !hop(this.#map, k) ){
+      if( !(k in this.#map) ){
+        ++this.#size;
         this.#keys = null;
       }
       this.#map[k] = ''+v;
     }
 
     removeItem(k){
-      if( delete this.#map[k] ){
+      if( k in this.#map ){
+        delete this.#map[k];
+        --this.#size;
         this.#keys = null;
       }
     }
@@ -242,10 +249,11 @@ globalThis.sqlite3ApiBootstrap.initializers.push(function(sqlite3){
     clear(){
       this.#map = Object.create(null);
       this.#keys = null;
+      this.#size = 0;
     }
 
     get length() {
-      return this.#getKeys().length;
+      return this.#size;
     }
   }/*KVVfsStorage*/;
 
diff --git a/manifest b/manifest
index 387c312553..dc7a3fcadc 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Fix\stypos\sin\sthe\sSQLITE_PREPARE_FROM_DDL\sdocumentation.
-D 2026-02-26T16:19:21.240
+C JS:\sslight\sperformance\simprovements\sin\sKVVfsStorage.
+D 2026-02-27T03:21:47.234
 F .fossil-settings/binary-glob 61195414528fb3ea9693577e1980230d78a1f8b0a54c78cf1b9b24d0a409ed6a x
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
@@ -603,7 +603,7 @@ F ext/wasm/api/sqlite3-api-worker1.c-pp.js 1041dd645e8e821c082b628cd8d9acf70c667
 F ext/wasm/api/sqlite3-license-version-header.js 98d90255a12d02214db634e041c8e7f2f133d9361a8ebf000ba9c9af4c6761cc
 F ext/wasm/api/sqlite3-opfs-async-proxy.js 92d6d327a862f1627ff3e88e60fdfea9def06ad539d98929ba46490e64372736
 F ext/wasm/api/sqlite3-vfs-helper.c-pp.js 3f828cc66758acb40e9c5b4dcfd87fd478a14c8fb7f0630264e6c7fa0e57515d
-F ext/wasm/api/sqlite3-vfs-kvvfs.c-pp.js 17b16db29e2e0c75d00f675c17710539269e30f853da6bac9044879e298c270f
+F ext/wasm/api/sqlite3-vfs-kvvfs.c-pp.js 7f55954f5965d84d8de9e3edbe3a9010198e7964da10f6a6f740f06d4c67ed40
 F ext/wasm/api/sqlite3-vfs-opfs-sahpool.c-pp.js 1575ea6bbcf2da1e6df6892c17521a0c1c1c199a672e9090176ea0b88de48bd9
 F ext/wasm/api/sqlite3-vfs-opfs.c-pp.js 88ce2078267a2d1af57525a32d896295f4a8db7664de0e17e82dc9ff006ed8d3
 F ext/wasm/api/sqlite3-vtab-helper.c-pp.js 366596d8ff73d4cefb938bbe95bc839d503c3fab6c8335ce4bf52f0d8a7dee81
@@ -2195,8 +2195,8 @@ F tool/warnings-clang.sh bbf6a1e685e534c92ec2bfba5b1745f34fb6f0bc2a362850723a9ee
 F tool/warnings.sh d924598cf2f55a4ecbc2aeb055c10bd5f48114793e7ba25f9585435da29e7e98
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
 F tool/winmain.c 00c8fb88e365c9017db14c73d3c78af62194d9644feaf60e220ab0f411f3604c
-P c3288f16848866a2c846221c33631785f7b39938078bb95c61895f789395aa1d
-R dcd62261fc7d31c8a65dd3cc5d14fd76
-U drh
-Z de1179cfcfccba649912303467a12236
+P 9174e7dacf867c1f80e73ccf5e0ee7b9e84fbe9f2e53559d06b72206b1cde3c6
+R 73e280751e913525512dae1e58b75d8d
+U stephan
+Z 6b9092990679409a5bbdeb3b4b80a0ab
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index 1a18fe1258..e8a6088f02 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-9174e7dacf867c1f80e73ccf5e0ee7b9e84fbe9f2e53559d06b72206b1cde3c6
+56edf2addb155dbb60269fe563ecb5f6132672c6c61f6f9d18ebdff72111298d