diff --git a/cjs/index.js b/cjs/index.js
index fdfe49c..5c5513d 100644
--- a/cjs/index.js
+++ b/cjs/index.js
@@ -1,13 +1,15 @@
 'use strict';
 const {
-  createReadStream, stat, mkdir, readFile, unlink, existsSync, writeFileSync, watchFile, unwatchFile
+  createReadStream, mkdir, unlink, existsSync, writeFileSync, watch
 } = require('fs');
 const {tmpdir} = require('os');
 const {dirname, extname, join, resolve} = require('path');
 
 const ucompress = (m => m.__esModule ? /* istanbul ignore next */ m.default : /* istanbul ignore next */ m)(require('ucompress'));
 
-const {parse} = JSON;
+const json = (m => m.__esModule ? /* istanbul ignore next */ m.default : /* istanbul ignore next */ m)(require('./json.js'));
+const stat = (m => m.__esModule ? /* istanbul ignore next */ m.default : /* istanbul ignore next */ m)(require('./stat.js'));
+
 const {compressed} = ucompress;
 
 const getPath = source => (source[0] === '/' ? source : resolve(source));
@@ -18,15 +20,12 @@ const internalServerError = res => {
   res.end();
 };
 
-const readAndServe = (res, asset, IfNoneMatch) => {
-  readFile(asset + '.json', (err, data) => {
+const readAndServe = (res, asset, cacheTimeout, IfNoneMatch) =>
+  json(asset, cacheTimeout).then(
+    headers => serveFile(res, asset, headers, IfNoneMatch),
     /* istanbul ignore next */
-    if (err)
-      internalServerError(res);
-    else
-      serveFile(res, asset, parse(data), IfNoneMatch);
-  });
-};
+    () => internalServerError(res)
+  );
 
 const serveFile = (res, asset, headers, IfNoneMatch) => {
   if (headers.ETag === IfNoneMatch) {
@@ -42,15 +41,95 @@ const streamFile = (res, asset, headers) => {
   createReadStream(asset).pipe(res);
 };
 
-module.exports = ({source, dest, headers}) => {
+module.exports = ({source, dest, headers, cacheTimeout: CT}) => {
   const SOURCE = getPath(source);
   const DEST = dest ? getPath(dest) : join(tmpdir(), 'ucdn');
   const options = {createFiles: true, headers};
   return (req, res, next) => {
     const path = req.url.replace(/\?.*$/, '');
     const original = SOURCE + path;
-    stat(original, (err, stats) => {
-      if (err || !stats.isFile()) {
+    stat(original, CT).then(
+      ({lastModified, size}) => {
+        if (path === '/favicon.ico')
+          streamFile(res, original, {
+            'Content-Length': size,
+            'Content-Type': 'image/vnd.microsoft.icon',
+            ...headers
+          });
+        else {
+          let asset = DEST + path;
+          let compression = '';
+          const {
+            ['accept-encoding']: AcceptEncoding,
+            ['if-none-match']: IfNoneMatch,
+            ['if-modified-since']: IfModifiedSince
+          } = req.headers;
+          if (compressed.has(extname(path).toLowerCase())) {
+            switch (true) {
+              /* istanbul ignore next */
+              case /\bbr\b/.test(AcceptEncoding):
+                compression = '.br';
+                break;
+              case /\bgzip\b/.test(AcceptEncoding):
+                compression = '.gzip';
+                break;
+              /* istanbul ignore next */
+              case /\bdeflate\b/.test(AcceptEncoding):
+                compression = '.deflate';
+                break;
+            }
+            asset += compression;
+          }
+          const create = () => {
+            const {length} = compression;
+            const compress = length ? asset.slice(0, -length) : asset;
+            const waitForIt = compress + '.wait';
+            mkdir(dirname(waitForIt), {recursive: true}, err => {
+              /* istanbul ignore if */
+              if (err)
+                internalServerError(res);
+              else if (existsSync(waitForIt))
+                watch(waitForIt, andClose).on(
+                  'close',
+                  () => readAndServe(res, asset, CT, IfNoneMatch)
+                );
+              else {
+                try {
+                  writeFileSync(waitForIt, path);
+                  ucompress(original, compress, options)
+                    .then(
+                      () => {
+                        unlink(waitForIt, err => {
+                          /* istanbul ignore if */
+                          if (err)
+                            internalServerError(res);
+                          else
+                            readAndServe(res, asset, CT, IfNoneMatch);
+                        });
+                      },
+                      /* istanbul ignore next */
+                      () => unlink(waitForIt, () => internalServerError(res))
+                    );
+                }
+                catch (o_O) {
+                  /* istanbul ignore next */
+                  internalServerError(res);
+                }
+              }
+            });
+          };
+          json(asset, CT).then(
+            headers => {
+              if (lastModified === IfModifiedSince)
+                serveFile(res, asset, headers, IfNoneMatch);
+              else
+                create();
+            },
+            create
+          );
+        }
+      },
+      () => {
         if (next)
           next();
         else {
@@ -58,83 +137,10 @@ module.exports = ({source, dest, headers}) => {
           res.end();
         }
       }
-      else if (path === '/favicon.ico')
-        streamFile(res, original, {
-          'Content-Length': stats.size,
-          'Content-Type': 'image/vnd.microsoft.icon',
-          ...headers
-        });
-      else {
-        let asset = DEST + path;
-        let compression = '';
-        const {
-          ['accept-encoding']: AcceptEncoding,
-          ['if-none-match']: IfNoneMatch,
-          ['if-modified-since']: IfModifiedSince
-        } = req.headers;
-        if (compressed.has(extname(path).toLowerCase())) {
-          switch (true) {
-            /* istanbul ignore next */
-            case /\bbr\b/.test(AcceptEncoding):
-              compression = '.br';
-              break;
-            case /\bgzip\b/.test(AcceptEncoding):
-              compression = '.gzip';
-              break;
-            /* istanbul ignore next */
-            case /\bdeflate\b/.test(AcceptEncoding):
-              compression = '.deflate';
-              break;
-          }
-          asset += compression;
-        }
-        readFile(asset + '.json', (err, data) => {
-          // if there was no error, be sure the source file is still the same
-          if (!err) {
-            if (new Date(stats.mtimeMs).toUTCString() === IfModifiedSince) {
-              serveFile(res, asset, parse(data), IfNoneMatch);
-              return;
-            }
-          }
-          // if the file was modified, re-optimize it, assuming it changed too
-          const {length} = compression;
-          const compress = length ? asset.slice(0, -length) : asset;
-          const waitForIt = compress + '.wait';
-          mkdir(dirname(waitForIt), {recursive: true}, err => {
-            /* istanbul ignore next */
-            if (err)
-              internalServerError(res);
-            else if (existsSync(waitForIt))
-              watchFile(waitForIt, () => {
-                unwatchFile(waitForIt);
-                readAndServe(res, asset, IfNoneMatch);
-              });
-            else {
-              try {
-                writeFileSync(waitForIt, path);
-                ucompress(original, compress, options)
-                  .then(
-                    () => {
-                      unlink(waitForIt, err => {
-                        /* istanbul ignore next */
-                        if (err)
-                          internalServerError(res);
-                        else
-                          readAndServe(res, asset, IfNoneMatch);
-                      });
-                    },
-                    /* istanbul ignore next */
-                    () => unlink(waitForIt, () => internalServerError(res))
-                  );
-              }
-              catch (o_O) {
-                /* istanbul ignore next */
-                internalServerError(res);
-              }
-            }
-          });
-        });
-      }
-    });
+    );
   };
 };
+
+function andClose() {
+  this.close();
+}
diff --git a/cjs/json.js b/cjs/json.js
new file mode 100644
index 0000000..e5b1efe
--- /dev/null
+++ b/cjs/json.js
@@ -0,0 +1,29 @@
+'use strict';
+const {readFile} = require('fs');
+
+const umap = (m => m.__esModule ? /* istanbul ignore next */ m.default : /* istanbul ignore next */ m)(require('umap'));
+
+const {parse} = JSON;
+
+const _ = new Map;
+const $ = umap(_);
+
+const clear = asset => {
+  _.delete(asset);
+};
+
+module.exports = (asset, timeout = 1000) => (
+  $.get(asset) ||
+  $.set(asset, new Promise((res, rej) => {
+    readFile(asset + '.json', (err, data) => {
+      if (err) {
+        _.delete(asset);
+        rej();
+      }
+      else {
+        res(parse(data));
+        setTimeout(clear, timeout, asset);
+      }
+    });
+  }))
+);
diff --git a/cjs/stat.js b/cjs/stat.js
new file mode 100644
index 0000000..1175034
--- /dev/null
+++ b/cjs/stat.js
@@ -0,0 +1,30 @@
+'use strict';
+const {stat} = require('fs');
+
+const umap = (m => m.__esModule ? /* istanbul ignore next */ m.default : /* istanbul ignore next */ m)(require('umap'));
+
+const _ = new Map;
+const $ = umap(_);
+
+const clear = asset => {
+  _.delete(asset);
+};
+
+module.exports = (asset, timeout = 1000) => (
+  $.get(asset) ||
+  $.set(asset, new Promise((res, rej) => {
+    stat(asset, (err, stats) => {
+      if (err || !stats.isFile()) {
+        _.delete(asset);
+        rej();
+      }
+      else {
+        setTimeout(clear, timeout, asset);
+        res({
+          lastModified: new Date(stats.mtimeMs).toUTCString(),
+          size: stats.size
+        });
+      }
+    });
+  }))
+);
diff --git a/esm/index.js b/esm/index.js
index 30e9a2a..7a52fea 100644
--- a/esm/index.js
+++ b/esm/index.js
@@ -1,14 +1,15 @@
 import {
-  createReadStream, stat, mkdir, readFile, unlink,
-  existsSync, writeFileSync,
-  watchFile, unwatchFile
+  createReadStream, mkdir, unlink,
+  existsSync, writeFileSync, watch
 } from 'fs';
 import {tmpdir} from 'os';
 import {dirname, extname, join, resolve} from 'path';
 
 import ucompress from 'ucompress';
 
-const {parse} = JSON;
+import json from './json.js';
+import stat from './stat.js';
+
 const {compressed} = ucompress;
 
 const getPath = source => (source[0] === '/' ? source : resolve(source));
@@ -19,15 +20,12 @@ const internalServerError = res => {
   res.end();
 };
 
-const readAndServe = (res, asset, IfNoneMatch) => {
-  readFile(asset + '.json', (err, data) => {
+const readAndServe = (res, asset, cacheTimeout, IfNoneMatch) =>
+  json(asset, cacheTimeout).then(
+    headers => serveFile(res, asset, headers, IfNoneMatch),
     /* istanbul ignore next */
-    if (err)
-      internalServerError(res);
-    else
-      serveFile(res, asset, parse(data), IfNoneMatch);
-  });
-};
+    () => internalServerError(res)
+  );
 
 const serveFile = (res, asset, headers, IfNoneMatch) => {
   if (headers.ETag === IfNoneMatch) {
@@ -43,15 +41,95 @@ const streamFile = (res, asset, headers) => {
   createReadStream(asset).pipe(res);
 };
 
-export default ({source, dest, headers}) => {
+export default ({source, dest, headers, cacheTimeout: CT}) => {
   const SOURCE = getPath(source);
   const DEST = dest ? getPath(dest) : join(tmpdir(), 'ucdn');
   const options = {createFiles: true, headers};
   return (req, res, next) => {
     const path = req.url.replace(/\?.*$/, '');
     const original = SOURCE + path;
-    stat(original, (err, stats) => {
-      if (err || !stats.isFile()) {
+    stat(original, CT).then(
+      ({lastModified, size}) => {
+        if (path === '/favicon.ico')
+          streamFile(res, original, {
+            'Content-Length': size,
+            'Content-Type': 'image/vnd.microsoft.icon',
+            ...headers
+          });
+        else {
+          let asset = DEST + path;
+          let compression = '';
+          const {
+            ['accept-encoding']: AcceptEncoding,
+            ['if-none-match']: IfNoneMatch,
+            ['if-modified-since']: IfModifiedSince
+          } = req.headers;
+          if (compressed.has(extname(path).toLowerCase())) {
+            switch (true) {
+              /* istanbul ignore next */
+              case /\bbr\b/.test(AcceptEncoding):
+                compression = '.br';
+                break;
+              case /\bgzip\b/.test(AcceptEncoding):
+                compression = '.gzip';
+                break;
+              /* istanbul ignore next */
+              case /\bdeflate\b/.test(AcceptEncoding):
+                compression = '.deflate';
+                break;
+            }
+            asset += compression;
+          }
+          const create = () => {
+            const {length} = compression;
+            const compress = length ? asset.slice(0, -length) : asset;
+            const waitForIt = compress + '.wait';
+            mkdir(dirname(waitForIt), {recursive: true}, err => {
+              /* istanbul ignore if */
+              if (err)
+                internalServerError(res);
+              else if (existsSync(waitForIt))
+                watch(waitForIt, andClose).on(
+                  'close',
+                  () => readAndServe(res, asset, CT, IfNoneMatch)
+                );
+              else {
+                try {
+                  writeFileSync(waitForIt, path);
+                  ucompress(original, compress, options)
+                    .then(
+                      () => {
+                        unlink(waitForIt, err => {
+                          /* istanbul ignore if */
+                          if (err)
+                            internalServerError(res);
+                          else
+                            readAndServe(res, asset, CT, IfNoneMatch);
+                        });
+                      },
+                      /* istanbul ignore next */
+                      () => unlink(waitForIt, () => internalServerError(res))
+                    );
+                }
+                catch (o_O) {
+                  /* istanbul ignore next */
+                  internalServerError(res);
+                }
+              }
+            });
+          };
+          json(asset, CT).then(
+            headers => {
+              if (lastModified === IfModifiedSince)
+                serveFile(res, asset, headers, IfNoneMatch);
+              else
+                create();
+            },
+            create
+          );
+        }
+      },
+      () => {
         if (next)
           next();
         else {
@@ -59,83 +137,10 @@ export default ({source, dest, headers}) => {
           res.end();
         }
       }
-      else if (path === '/favicon.ico')
-        streamFile(res, original, {
-          'Content-Length': stats.size,
-          'Content-Type': 'image/vnd.microsoft.icon',
-          ...headers
-        });
-      else {
-        let asset = DEST + path;
-        let compression = '';
-        const {
-          ['accept-encoding']: AcceptEncoding,
-          ['if-none-match']: IfNoneMatch,
-          ['if-modified-since']: IfModifiedSince
-        } = req.headers;
-        if (compressed.has(extname(path).toLowerCase())) {
-          switch (true) {
-            /* istanbul ignore next */
-            case /\bbr\b/.test(AcceptEncoding):
-              compression = '.br';
-              break;
-            case /\bgzip\b/.test(AcceptEncoding):
-              compression = '.gzip';
-              break;
-            /* istanbul ignore next */
-            case /\bdeflate\b/.test(AcceptEncoding):
-              compression = '.deflate';
-              break;
-          }
-          asset += compression;
-        }
-        readFile(asset + '.json', (err, data) => {
-          // if there was no error, be sure the source file is still the same
-          if (!err) {
-            if (new Date(stats.mtimeMs).toUTCString() === IfModifiedSince) {
-              serveFile(res, asset, parse(data), IfNoneMatch);
-              return;
-            }
-          }
-          // if the file was modified, re-optimize it, assuming it changed too
-          const {length} = compression;
-          const compress = length ? asset.slice(0, -length) : asset;
-          const waitForIt = compress + '.wait';
-          mkdir(dirname(waitForIt), {recursive: true}, err => {
-            /* istanbul ignore next */
-            if (err)
-              internalServerError(res);
-            else if (existsSync(waitForIt))
-              watchFile(waitForIt, () => {
-                unwatchFile(waitForIt);
-                readAndServe(res, asset, IfNoneMatch);
-              });
-            else {
-              try {
-                writeFileSync(waitForIt, path);
-                ucompress(original, compress, options)
-                  .then(
-                    () => {
-                      unlink(waitForIt, err => {
-                        /* istanbul ignore next */
-                        if (err)
-                          internalServerError(res);
-                        else
-                          readAndServe(res, asset, IfNoneMatch);
-                      });
-                    },
-                    /* istanbul ignore next */
-                    () => unlink(waitForIt, () => internalServerError(res))
-                  );
-              }
-              catch (o_O) {
-                /* istanbul ignore next */
-                internalServerError(res);
-              }
-            }
-          });
-        });
-      }
-    });
+    );
   };
 };
+
+function andClose() {
+  this.close();
+}
diff --git a/esm/json.js b/esm/json.js
new file mode 100644
index 0000000..aded27b
--- /dev/null
+++ b/esm/json.js
@@ -0,0 +1,28 @@
+import {readFile} from 'fs';
+
+import umap from 'umap';
+
+const {parse} = JSON;
+
+const _ = new Map;
+const $ = umap(_);
+
+const clear = asset => {
+  _.delete(asset);
+};
+
+export default (asset, timeout = 1000) => (
+  $.get(asset) ||
+  $.set(asset, new Promise((res, rej) => {
+    readFile(asset + '.json', (err, data) => {
+      if (err) {
+        _.delete(asset);
+        rej();
+      }
+      else {
+        res(parse(data));
+        setTimeout(clear, timeout, asset);
+      }
+    });
+  }))
+);
diff --git a/esm/stat.js b/esm/stat.js
new file mode 100644
index 0000000..4b2c56d
--- /dev/null
+++ b/esm/stat.js
@@ -0,0 +1,29 @@
+import {stat} from 'fs';
+
+import umap from 'umap';
+
+const _ = new Map;
+const $ = umap(_);
+
+const clear = asset => {
+  _.delete(asset);
+};
+
+export default (asset, timeout = 1000) => (
+  $.get(asset) ||
+  $.set(asset, new Promise((res, rej) => {
+    stat(asset, (err, stats) => {
+      if (err || !stats.isFile()) {
+        _.delete(asset);
+        rej();
+      }
+      else {
+        setTimeout(clear, timeout, asset);
+        res({
+          lastModified: new Date(stats.mtimeMs).toUTCString(),
+          size: stats.size
+        });
+      }
+    });
+  }))
+);
diff --git a/package.json b/package.json
index 3c92e2d..82c24ef 100644
--- a/package.json
+++ b/package.json
@@ -7,7 +7,7 @@
     "build": "npm run cjs && npm run test",
     "cjs": "ascjs --no-default esm cjs",
     "coveralls": "nyc report --reporter=text-lcov | coveralls",
-    "test": "rm -rf test/dest && nyc node test/index.js"
+    "test": "rm -rf test/dest && nyc node test/index.js && rm test/index.test"
   },
   "keywords": [
     "ucompress",
diff --git a/test/index.js b/test/index.js
index fb6c4d3..0efa8e1 100644
--- a/test/index.js
+++ b/test/index.js
@@ -148,6 +148,7 @@ Promise.resolve('\x1b[1mµcdn\x1b[0m')
   }))
   .then(name => {
     requestHandler = cdn({
+      cacheTimeout: 100,
       source: './test/source'
     });
     return name;
@@ -215,5 +216,45 @@ Promise.resolve('\x1b[1mµcdn\x1b[0m')
       })
     );
   }))
+
+  .then(name => new Promise(resolve => {
+    console.log(name);
+    const path = '/benja-dark.svg';
+    const request = createRequest(path);
+    request.headers.acceptEncoding = '';
+    let i = 0;
+    const done = () => {
+      if (++i === 2)
+        resolve(path);
+    };
+    requestHandler(
+      request,
+      createResponse(operations => {
+        console.assert(operations.length === 2, 'correct amount of operations');
+        const [code, headers] = operations.shift();
+        const content = operations.shift();
+        console.assert(content.length < 1, 'correct content');
+        console.assert(code === 200, 'correct code');
+        console.assert(headers['Content-Length'] === 2478, 'correct length');
+        console.assert(headers['Content-Type'] === 'image/svg+xml', 'correct mime');
+        console.assert(headers['ETag'] === '"9ae-WAa0uuWT+I9+hj77"', 'correct ETag');
+        done();
+      })
+    );
+    requestHandler(
+      request,
+      createResponse(operations => {
+        console.assert(operations.length === 2, 'correct amount of operations');
+        const [code, headers] = operations.shift();
+        const content = operations.shift();
+        console.assert(content.length < 1, 'correct content');
+        console.assert(code === 200, 'correct code');
+        console.assert(headers['Content-Length'] === 2478, 'correct length');
+        console.assert(headers['Content-Type'] === 'image/svg+xml', 'correct mime');
+        console.assert(headers['ETag'] === '"9ae-WAa0uuWT+I9+hj77"', 'correct ETag');
+        done();
+      })
+    );
+  }))
   .then(console.log)
 ;
diff --git a/test/index.test b/test/index.test
deleted file mode 100644
index ea71b61..0000000
Binary files a/test/index.test and /dev/null differ
diff --git a/test/server.cjs b/test/server.cjs
index abd331e..60aa6f6 100644
--- a/test/server.cjs
+++ b/test/server.cjs
@@ -3,6 +3,7 @@ const {join} = require('path');
 
 const cdn = require('../cjs');
 const callback = cdn({
+  cacheTimeout: 10000,
   source: join(__dirname, 'source'),
   dest: join(__dirname, 'dest')
 });