diff --git a/package.json b/package.json
index 4cdfd6c..4e21fdc 100644
--- a/package.json
+++ b/package.json
@@ -27,8 +27,7 @@
     "@csstools/css-calc": "^3.1.1",
     "@csstools/css-color-parser": "^4.0.2",
     "@csstools/css-parser-algorithms": "^4.0.0",
-    "@csstools/css-tokenizer": "^4.0.0",
-    "lru-cache": "^11.2.7"
+    "@csstools/css-tokenizer": "^4.0.0"
   },
   "devDependencies": {
     "@tanstack/vite-config": "^0.5.2",
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 99124df..6e90ca3 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -33,9 +33,6 @@ importers:
       '@csstools/css-tokenizer':
         specifier: ^4.0.0
         version: 4.0.0
-      lru-cache:
-        specifier: ^11.2.7
-        version: 11.2.7
     devDependencies:
       '@tanstack/vite-config':
         specifier: ^0.5.2
diff --git a/src/js/cache.ts b/src/js/cache.ts
index 1bbf1ed..8b159f5 100644
--- a/src/js/cache.ts
+++ b/src/js/cache.ts
@@ -2,7 +2,6 @@
  * cache
  */
 
-import { LRUCache } from 'lru-cache';
 import { Options } from './typedef';
 
 /* numeric constants */
@@ -45,12 +44,63 @@ export class NullObject extends CacheItem {
   }
 }
 
+/**
+ * Generational Cache implementation
+ */
+export class GenerationalCache<K, V> {
+  private max: number;
+  private current: Map<K, V>;
+  private old: Map<K, V>;
+
+  constructor(max: number) {
+    this.max = Math.ceil(max / 2);
+    this.current = new Map<K, V>();
+    this.old = new Map<K, V>();
+  }
+
+  get(key: K): V | undefined {
+    let value = this.current.get(key);
+    if (value !== undefined) {
+      return value;
+    }
+
+    value = this.old.get(key);
+    if (value !== undefined) {
+      this.set(key, value);
+      return value;
+    }
+
+    return undefined;
+  }
+
+  set(key: K, value: V): void {
+    this.current.set(key, value);
+
+    if (this.current.size >= this.max) {
+      this.old = this.current;
+      this.current = new Map<K, V>();
+    }
+  }
+
+  has(key: K): boolean {
+    return this.current.has(key) || this.old.has(key);
+  }
+
+  delete(key: K): void {
+    this.current.delete(key);
+    this.old.delete(key);
+  }
+
+  clear(): void {
+    this.current.clear();
+    this.old.clear();
+  }
+}
+
 /*
- * lru cache
+ * generational cache instance
  */
-export const lruCache = new LRUCache({
-  max: MAX_CACHE
-});
+export const genCache = new GenerationalCache<string, CacheItem>(MAX_CACHE);
 
 /**
  * set cache
@@ -61,11 +111,11 @@ export const lruCache = new LRUCache({
 export const setCache = (key: string, value: unknown): void => {
   if (key) {
     if (value === null) {
-      lruCache.set(key, new NullObject());
+      genCache.set(key, new NullObject());
     } else if (value instanceof CacheItem) {
-      lruCache.set(key, value);
+      genCache.set(key, value);
     } else {
-      lruCache.set(key, new CacheItem(value));
+      genCache.set(key, new CacheItem(value));
     }
   }
 };
@@ -76,13 +126,13 @@ export const setCache = (key: string, value: unknown): void => {
  * @returns cached item or false otherwise
  */
 export const getCache = (key: string): CacheItem | boolean => {
-  if (key && lruCache.has(key)) {
-    const item = lruCache.get(key);
+  if (key && genCache.has(key)) {
+    const item = genCache.get(key);
     if (item instanceof CacheItem) {
       return item;
     }
     // delete unexpected cached item
-    lruCache.delete(key);
+    genCache.delete(key);
     return false;
   }
   return false;
diff --git a/test/cache.test.ts b/test/cache.test.ts
index e1e7ac3..bcf21bf 100644
--- a/test/cache.test.ts
+++ b/test/cache.test.ts
@@ -6,18 +6,17 @@
 import { afterEach, assert, beforeEach, describe, it } from 'vitest';
 
 /* test */
-import { LRUCache } from 'lru-cache';
 import * as cache from '../src/js/cache';
 
-describe('lru cache', () => {
+describe('generational cache', () => {
   it('should be instance', () => {
-    const { lruCache } = cache;
-    assert.strictEqual(lruCache instanceof LRUCache, true, 'instance');
-    assert.strictEqual(typeof lruCache.clear, 'function', 'clear');
-    assert.strictEqual(typeof lruCache.delete, 'function', 'delete');
-    assert.strictEqual(typeof lruCache.get, 'function', 'get');
-    assert.strictEqual(typeof lruCache.has, 'function', 'has');
-    assert.strictEqual(typeof lruCache.set, 'function', 'set');
+    const { GenerationalCache, genCache } = cache;
+    assert.strictEqual(genCache instanceof GenerationalCache, true, 'instance');
+    assert.strictEqual(typeof genCache.clear, 'function', 'clear');
+    assert.strictEqual(typeof genCache.delete, 'function', 'delete');
+    assert.strictEqual(typeof genCache.get, 'function', 'get');
+    assert.strictEqual(typeof genCache.has, 'function', 'has');
+    assert.strictEqual(typeof genCache.set, 'function', 'set');
   });
 });
 
@@ -58,55 +57,55 @@ describe('NullObject', () => {
 });
 
 describe('set cache', () => {
-  const { CacheItem, lruCache } = cache;
+  const { CacheItem, genCache } = cache;
   const func = cache.setCache;
 
   beforeEach(() => {
-    lruCache.clear();
+    genCache.clear();
   });
   afterEach(() => {
-    lruCache.clear();
+    genCache.clear();
   });
 
   it('should not set cache', () => {
     func('');
-    assert.strictEqual(lruCache.has(''), false, 'has');
+    assert.strictEqual(genCache.has(''), false, 'has');
   });
 
   it('should set cache', () => {
     func('foo');
-    assert.strictEqual(lruCache.has('foo'), true, 'has');
-    assert.strictEqual(lruCache.get('foo') instanceof CacheItem, true, 'cache');
+    assert.strictEqual(genCache.has('foo'), true, 'has');
+    assert.strictEqual(genCache.get('foo') instanceof CacheItem, true, 'cache');
   });
 
   it('should set cache', () => {
     func('bar', 'bar');
-    assert.strictEqual(lruCache.has('bar'), true, 'has');
-    assert.strictEqual(lruCache.get('bar') instanceof CacheItem, true, 'cache');
+    assert.strictEqual(genCache.has('bar'), true, 'has');
+    assert.strictEqual(genCache.get('bar') instanceof CacheItem, true, 'cache');
   });
 
   it('should set cache', () => {
     func('baz', null);
-    assert.strictEqual(lruCache.has('baz'), true, 'has');
-    assert.strictEqual(lruCache.get('baz') instanceof CacheItem, true, 'cache');
+    assert.strictEqual(genCache.has('baz'), true, 'has');
+    assert.strictEqual(genCache.get('baz') instanceof CacheItem, true, 'cache');
   });
 
   it('should set cache', () => {
     func('qux', new CacheItem('qux'));
-    assert.strictEqual(lruCache.has('qux'), true, 'has');
-    assert.strictEqual(lruCache.get('qux') instanceof CacheItem, true, 'cache');
+    assert.strictEqual(genCache.has('qux'), true, 'has');
+    assert.strictEqual(genCache.get('qux') instanceof CacheItem, true, 'cache');
   });
 });
 
 describe('get cache', () => {
-  const { CacheItem, NullObject, lruCache, setCache } = cache;
+  const { CacheItem, NullObject, genCache, setCache } = cache;
   const func = cache.getCache;
 
   beforeEach(() => {
-    lruCache.clear();
+    genCache.clear();
   });
   afterEach(() => {
-    lruCache.clear();
+    genCache.clear();
   });
 
   it('should get cache', () => {
@@ -138,9 +137,9 @@ describe('get cache', () => {
   });
 
   it('should get false and delete key', () => {
-    lruCache.set('quux', 'quux');
+    genCache.set('quux', 'quux');
     const res = func('quux');
-    assert.strictEqual(lruCache.has('quux'), false, 'key');
+    assert.strictEqual(genCache.has('quux'), false, 'key');
     assert.strictEqual(res, false, 'result');
   });
 });
diff --git a/test/color.test.ts b/test/color.test.ts
index dc9e96d..fe61894 100644
--- a/test/color.test.ts
+++ b/test/color.test.ts
@@ -6,14 +6,14 @@
 import { afterEach, assert, beforeEach, describe, it } from 'vitest';
 
 /* test */
-import { NullObject, lruCache } from '../src/js/cache';
+import { NullObject, genCache } from '../src/js/cache';
 import * as color from '../src/js/color';
 
 beforeEach(() => {
-  lruCache.clear();
+  genCache.clear();
 });
 afterEach(() => {
-  lruCache.clear();
+  genCache.clear();
 });
 
 describe('cache invalid color value', () => {
diff --git a/test/convert.test.ts b/test/convert.test.ts
index be8bd3d..b0d3a90 100644
--- a/test/convert.test.ts
+++ b/test/convert.test.ts
@@ -7,14 +7,14 @@ import { afterEach, assert, beforeEach, describe, it } from 'vitest';
 
 /* test */
 import * as convert from '../src/js/convert.js';
-import { lruCache } from '../src/js/cache.js';
+import { genCache } from '../src/js/cache.js';
 
 beforeEach(() => {
-  lruCache.clear();
+  genCache.clear();
 });
 
 afterEach(() => {
-  lruCache.clear();
+  genCache.clear();
 });
 
 describe('pre process', () => {
diff --git a/test/css-calc.test.ts b/test/css-calc.test.ts
index 7800c2e..cd37670 100644
--- a/test/css-calc.test.ts
+++ b/test/css-calc.test.ts
@@ -6,15 +6,15 @@
 import { afterEach, assert, beforeEach, describe, it } from 'vitest';
 
 /* test */
-import { lruCache } from '../src/js/cache';
+import { genCache } from '../src/js/cache';
 import * as csscalc from '../src/js/css-calc';
 
 beforeEach(() => {
-  lruCache.clear();
+  genCache.clear();
 });
 
 afterEach(() => {
-  lruCache.clear();
+  genCache.clear();
 });
 
 describe('Calculator', () => {
diff --git a/test/css-gradient.test.ts b/test/css-gradient.test.ts
index 23f2bb9..d1452a4 100644
--- a/test/css-gradient.test.ts
+++ b/test/css-gradient.test.ts
@@ -6,15 +6,15 @@
 import { afterEach, assert, beforeEach, describe, it } from 'vitest';
 
 /* test */
-import { lruCache } from '../src/js/cache';
+import { genCache } from '../src/js/cache';
 import * as grad from '../src/js/css-gradient';
 
 beforeEach(() => {
-  lruCache.clear();
+  genCache.clear();
 });
 
 afterEach(() => {
-  lruCache.clear();
+  genCache.clear();
 });
 
 describe('get gradient type', () => {
diff --git a/test/css-var.test.ts b/test/css-var.test.ts
index f3cd9b4..7efd04c 100644
--- a/test/css-var.test.ts
+++ b/test/css-var.test.ts
@@ -6,15 +6,15 @@
 import { afterEach, assert, beforeEach, describe, it } from 'vitest';
 
 /* test */
-import { lruCache } from '../src/js/cache';
+import { genCache } from '../src/js/cache';
 import * as custom from '../src/js/css-var';
 
 beforeEach(() => {
-  lruCache.clear();
+  genCache.clear();
 });
 
 afterEach(() => {
-  lruCache.clear();
+  genCache.clear();
 });
 
 describe('resolve CSS variable', () => {
diff --git a/test/relative-color.test.ts b/test/relative-color.test.ts
index d1b37d2..dd5a7d5 100644
--- a/test/relative-color.test.ts
+++ b/test/relative-color.test.ts
@@ -7,15 +7,15 @@ import { tokenize } from '@csstools/css-tokenizer';
 import { afterEach, assert, beforeEach, describe, it } from 'vitest';
 
 /* test */
-import { lruCache } from '../src/js/cache';
+import { genCache } from '../src/js/cache';
 import * as relColor from '../src/js/relative-color';
 
 beforeEach(() => {
-  lruCache.clear();
+  genCache.clear();
 });
 
 afterEach(() => {
-  lruCache.clear();
+  genCache.clear();
 });
 
 describe('resolve relative color channels', () => {
diff --git a/test/resolve.test.ts b/test/resolve.test.ts
index 9cfc8c1..cd3ba1e 100644
--- a/test/resolve.test.ts
+++ b/test/resolve.test.ts
@@ -7,15 +7,15 @@ import { afterEach, assert, beforeEach, describe, it } from 'vitest';
 
 /* test */
 import * as api from '../src/js/resolve';
-import { lruCache } from '../src/js/cache';
+import { genCache } from '../src/js/cache';
 import { parseColorValue } from '../src/js/color';
 
 beforeEach(() => {
-  lruCache.clear();
+  genCache.clear();
 });
 
 afterEach(() => {
-  lruCache.clear();
+  genCache.clear();
 });
 
 describe('resolve CSS color', () => {
diff --git a/test/util.test.ts b/test/util.test.ts
index f1cfb6c..3f8eb89 100644
--- a/test/util.test.ts
+++ b/test/util.test.ts
@@ -6,15 +6,15 @@
 import { afterEach, assert, beforeEach, describe, it } from 'vitest';
 
 /* test */
-import { lruCache } from '../src/js/cache';
+import { genCache } from '../src/js/cache';
 import * as util from '../src/js/util';
 
 beforeEach(() => {
-  lruCache.clear();
+  genCache.clear();
 });
 
 afterEach(() => {
-  lruCache.clear();
+  genCache.clear();
 });
 
 describe('split value', () => {