diff --git a/README.md b/README.md
index f03c01a..31e3883 100644
--- a/README.md
+++ b/README.md
@@ -118,7 +118,7 @@ const fetchBuilder, { MemoryCache } = require('node-fetch-cache');
 const fetch = fetchBuilder.withCache(new MemoryCache(options));
 ```
 
-Supported options:
+Options:
 
 ```js
 {
@@ -140,6 +140,7 @@ const fetch = fetchBuilder.withCache(new FileSystemCache(options));
 
 ```js
 {
+  cacheDirectory: '/my/cache/directory/path', // Specify where to keep the cache. If undefined, '.cache' is used by default. If this directory does not exist, it will be created.
   ttl: 1000, // Time to live. How long (in ms) responses remain cached before being automatically ejected. If undefined, responses are never automatically ejected from the cache.
 }
 ```
diff --git a/classes/caching/file_system_cache.js b/classes/caching/file_system_cache.js
new file mode 100644
index 0000000..074c2d1
--- /dev/null
+++ b/classes/caching/file_system_cache.js
@@ -0,0 +1,29 @@
+const FPersist = require('fpersist');
+const KeyTimeout = require('./key_timeout.js');
+
+module.exports = class FileSystemCache {
+  constructor(options = {}) {
+    this.ttl = options.ttl;
+    this.keyTimeout = new KeyTimeout();
+
+    const cacheDirectory = options.cacheDirectory || '.cache';
+    this.cache = new FPersist(cacheDirectory);
+  }
+
+  get(key) {
+    return this.cache.getItem(key);
+  }
+
+  remove(key) {
+    this.keyTimeout.clearTimeout(key);
+    return this.cache.deleteItem(key);
+  }
+
+  async set(key, value) {
+    await this.cache.setItem(key, value);
+
+    if (typeof this.ttl === 'number') {
+      this.keyTimeout.updateTimeout(key, this.ttl, () => this.remove(key));
+    }
+  }
+}
diff --git a/classes/caching/key_timeout.js b/classes/caching/key_timeout.js
new file mode 100644
index 0000000..635c117
--- /dev/null
+++ b/classes/caching/key_timeout.js
@@ -0,0 +1,16 @@
+module.exports = class KeyTimeout {
+  constructor() {
+    this.timeoutHandleForKey = {};
+  }
+
+  clearTimeout(key) {
+    clearTimeout(this.timeoutHandleForKey[key]);
+  }
+
+  updateTimeout(key, durationMs, callback) {
+    this.clearTimeout(key);
+    this.timeoutHandleForKey[key] = setTimeout(() => {
+      callback();
+    }, durationMs);
+  }
+}
\ No newline at end of file
diff --git a/classes/caching/memory_cache.js b/classes/caching/memory_cache.js
new file mode 100644
index 0000000..9428f5d
--- /dev/null
+++ b/classes/caching/memory_cache.js
@@ -0,0 +1,33 @@
+const KeyTimeout = require('./key_timeout.js');
+
+module.exports = class MemoryCache {
+  constructor(options = {}) {
+    this.ttl = options.ttl;
+    this.keyTimeout = new KeyTimeout();
+
+    if (options.global && !globalThis.nodeFetchCache) {
+      globalThis.nodeFetchCache = {};
+    }
+
+    this.cache = options.global
+      ? globalThis.nodeFetchCache
+      : {};
+  }
+
+  get(key) {
+    return this.cache[key];
+  }
+
+  remove(key) {
+    this.keyTimeout.clearTimeout(key);
+    delete this.cache[key];
+  }
+
+  set(key, value) {
+    this.cache[key] = value;
+
+    if (typeof this.ttl === 'number') {
+      this.keyTimeout.updateTimeout(key, this.ttl, () => this.remove(key));
+    }
+  }
+}
diff --git a/classes/response.js b/classes/response.js
index b22443f..2f2c3e4 100644
--- a/classes/response.js
+++ b/classes/response.js
@@ -3,9 +3,9 @@ const stream = require('stream');
 const Headers = require('./headers.js');
 
 class Response {
-  constructor(raw, cacheFilePath, fromCache) {
+  constructor(raw, ejectSelfFromCache, fromCache) {
     Object.assign(this, raw);
-    this.cacheFilePath = cacheFilePath;
+    this.ejectSelfFromCache = ejectSelfFromCache;
     this.headers = new Headers(raw.headers);
     this.fromCache = fromCache;
     this.bodyUsed = false;
@@ -40,14 +40,8 @@ class Response {
     return this.consumeBody();
   }
 
-  async ejectFromCache() {
-    try {
-      await fs.promises.unlink(this.cacheFilePath);
-    } catch (err) {
-      if (err.code !== 'ENOENT') {
-        throw err;
-      }
-    }
+  ejectFromCache() {
+    return this.ejectSelfFromCache();
   }
 }
 
diff --git a/index.js b/index.js
index 6927106..2787119 100644
--- a/index.js
+++ b/index.js
@@ -4,6 +4,7 @@ const { URLSearchParams } = require('url');
 const crypto = require('crypto');
 const path = require('path');
 const Response = require('./classes/response.js');
+const MemoryCache = require('./classes/caching/memory_cache.js');
 
 const CACHE_VERSION = 2;
 
@@ -88,32 +89,27 @@ async function createRawResponse(fetchRes) {
   };
 }
 
-async function getResponse(cacheDirPath, requestArguments) {
+async function getResponse(cache, requestArguments) {
   const cacheKey = getCacheKey(requestArguments);
-  const cachedFilePath = path.join(cacheDirPath, `${cacheKey}.json`);
+  const cachedValue = await cache.get(cacheKey);
 
-  try {
-    const rawResponse = JSON.parse(await fs.promises.readFile(cachedFilePath));
-    return new Response(rawResponse, cachedFilePath, true);
-  } catch (err) {
+  const ejectSelfFromCache = () => cache.remove(cacheKey);
+
+  if (cachedValue) {
+    return new Response(cachedValue, ejectSelfFromCache, true);
+  } else {
     const fetchResponse = await fetch(...requestArguments);
     const rawResponse = await createRawResponse(fetchResponse);
-    await fs.promises.writeFile(cachedFilePath, JSON.stringify(rawResponse));
-    return new Response(rawResponse, cachedFilePath, false);
+    await cache.set(cacheKey, rawResponse);
+    return new Response(rawResponse, ejectSelfFromCache, false);
   }
 }
 
-function createFetch(cacheDirPath) {
-  let madeDir = false;
+function createFetchWithCache(cache) {
+  const fetch = (...args) => getResponse(cache, args);
+  fetch.withCache = createFetchWithCache;
 
-  return async (...args) => {
-    if (!madeDir) {
-      await fs.promises.mkdir(cacheDirPath, { recursive: true });
-      madeDir = true;
-    }
-
-    return getResponse(cacheDirPath, args);
-  };
+  return fetch;
 }
 
-module.exports = createFetch;
+module.exports = createFetchWithCache(new MemoryCache());
diff --git a/test/expected_png.png b/test/expected_png.png
new file mode 100644
index 0000000..cc0c128
Binary files /dev/null and b/test/expected_png.png differ
diff --git a/test/tests.js b/test/tests.js
index b1df47a..5223218 100644
--- a/test/tests.js
+++ b/test/tests.js
@@ -5,6 +5,7 @@ const rimraf = require('rimraf');
 const path = require('path');
 const FetchCache = require('../index.js');
 const { URLSearchParams } = require('url');
+const MemoryCache = require('../classes/caching/memory_cache.js');
 
 const CACHE_PATH = path.join(__dirname, '..', '.cache');
 const expectedPngBuffer = fs.readFileSync(path.join(__dirname, 'expected_png.png'));
@@ -28,7 +29,7 @@ function post(body) {
 
 beforeEach(async function() {
   rimraf.sync(CACHE_PATH);
-  fetch = FetchCache(CACHE_PATH);
+  fetch = FetchCache.withCache(new MemoryCache());
 });
 
 describe('Basic property tests', function() {