diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d4edf6c..4798f3b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -15,7 +15,7 @@ jobs:
       - name: Setup Node
         uses: actions/setup-node@v4
         with:
-          node-version: 18
+          node-version: 20
           cache: 'pnpm'
       - run: pnpm install --frozen-lockfile
       - run: pnpm test-with-emulator
@@ -31,7 +31,7 @@ jobs:
       - name: Setup Node
         uses: actions/setup-node@v4
         with:
-          node-version: 18
+          node-version: 20
           cache: 'pnpm'
       - run: pnpm install --frozen-lockfile
       - run: pnpm lint-fix
diff --git a/package.json b/package.json
index 85b02bf..553dba7 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "firebase-auth-cloudflare-workers-x509",
-  "version": "2.0.8",
+  "version": "2.0.9",
   "description": "Firebase auth library for Cloudflare Workers (forked from firebase-auth-cloudflare-workers and modified to use X.509 certificates)",
   "author": "ciscorn",
   "maintainers": [
@@ -69,5 +69,6 @@
   ],
   "bugs": {
     "url": "https://github.com/Code-Hex/firebase-auth-cloudflare-workers/issues"
-  }
+  },
+  "packageManager": "pnpm@9.9.0+sha512.60c18acd138bff695d339be6ad13f7e936eea6745660d4cc4a776d5247c540d0edee1a563695c183a66eb917ef88f2b4feb1fc25f32a7adcadc7aaf3438e99c1"
 }
diff --git a/src/index.ts b/src/index.ts
index 3b790b2..15a92f7 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -8,6 +8,7 @@ import { WorkersKVStore } from './key-store';
 export { type Credential, ServiceAccountCredential } from './credential';
 export { emulatorHost, useEmulator } from './emulator';
 export type { KeyStorer };
+export { InMemoryStore } from './key-store';
 export type { EmulatorEnv } from './emulator';
 export type { FirebaseIdToken } from './token-verifier';
 export type { RetryConfig };
diff --git a/src/key-store.ts b/src/key-store.ts
index 1cdcf19..74bb847 100644
--- a/src/key-store.ts
+++ b/src/key-store.ts
@@ -22,3 +22,19 @@ export class WorkersKVStore implements KeyStorer {
     });
   }
 }
+
+export class InMemoryStore implements KeyStorer {
+  private val: string | null = null;
+  private expireAt: number = 0;
+
+  async get() {
+    if (Date.now() > this.expireAt) {
+      this.val = null;
+    }
+    return this.val ? JSON.parse(this.val) : null;
+  }
+  async put(value: string, expirationTtl: number) {
+    this.expireAt = Date.now() + expirationTtl * 1000;
+    this.val = value;
+  }
+}
diff --git a/src/version.ts b/src/version.ts
index 34e65ae..8c3f849 100644
--- a/src/version.ts
+++ b/src/version.ts
@@ -1 +1 @@
-export const version = '2.0.7';
+export const version = '2.0.9';
diff --git a/tests/auth.test.ts b/tests/auth.test.ts
index c04a438..4bde8c3 100644
--- a/tests/auth.test.ts
+++ b/tests/auth.test.ts
@@ -4,7 +4,8 @@ import { BaseAuth } from '../src/auth';
 import { AuthApiClient } from '../src/auth-api-requests';
 import { AuthClientErrorCode, FirebaseAuthError } from '../src/errors';
 import type { UserRecord } from '../src/user-record';
-import type { EmulatorEnv, KeyStorer } from './../src/index';
+import { InMemoryStore } from './../src/index';
+import type { EmulatorEnv } from './../src/index';
 import {
   EmulatedSigner,
   FirebaseTokenGenerator,
@@ -34,7 +35,7 @@ describe('createSessionCookie()', () => {
 
   const signer = new EmulatedSigner();
   const tokenGenerator = new FirebaseTokenGenerator(signer);
-  const keyStorer = new InMemoryKeyStorer('cache-key');
+  const keyStorer = new InMemoryStore();
 
   it('creates a valid Firebase session cookie', async () => {
     const auth = new BaseAuth(projectId, keyStorer, new NopCredential());
@@ -128,7 +129,7 @@ describe('createSessionCookie()', () => {
 
 describe('verifySessionCookie()', () => {
   const uid = sessionCookieUids[0];
-  const keyStorer = new InMemoryKeyStorer('cache-key');
+  const keyStorer = new InMemoryStore();
   const auth = new BaseAuth(projectId, keyStorer, new NopCredential());
   const signer = new EmulatedSigner();
   const tokenGenerator = new FirebaseTokenGenerator(signer);
@@ -177,7 +178,7 @@ describe('getUser()', () => {
     admin: true,
     groupId: '1234',
   };
-  const keyStorer = new InMemoryKeyStorer('cache-key');
+  const keyStorer = new InMemoryStore();
   const auth = new BaseAuth(projectId, keyStorer, new NopCredential());
   const signer = new EmulatedSigner();
   const tokenGenerator = new FirebaseTokenGenerator(signer);
@@ -231,25 +232,6 @@ function generateRandomString(stringLength: number) {
   return randomString;
 }
 
-class InMemoryKeyStorer implements KeyStorer {
-  private store: Map<string, unknown> = new Map();
-  private timerId: NodeJS.Timeout | null = null;
-
-  constructor(private readonly cacheKey: string) {}
-
-  public async get<ExpectedValue = unknown>(): Promise<ExpectedValue | null> {
-    return (this.store.get(this.cacheKey) as ExpectedValue) || null;
-  }
-
-  public async put(value: string, expirationTtl: number): Promise<void> {
-    if (this.timerId) {
-      clearTimeout(this.timerId);
-    }
-    this.store.set(this.cacheKey, value);
-    this.timerId = setTimeout(() => this.store.delete(this.cacheKey), expirationTtl * 1000);
-  }
-}
-
 const FIREBASE_AUTH_DISABLE_USER = new ApiSettings('v1', '/accounts:update', 'POST')
   // Set response validator.
   .setResponseValidator((response: any) => {