diff --git a/serve.py b/serve.py
index 2238540..6562bf1 100755
--- a/serve.py
+++ b/serve.py
@@ -1,25 +1,26 @@
 #!/usr/bin/env python3
 
-# base
+# python standard library
 from os import path
 import sys
-import argparse
-import logging.config
-import json
 import base64
 import uuid
+import logging.config
+import argparse
 import mimetypes
 import signal
+import asyncio
+import json
 
-# packages
+# user installed libraries
 import tornado.ioloop
 import tornado.web
 import tornado.httpserver
 from tornado import template, gen
 
-# project
-from tools import load_yaml, md_to_html
+# this project
 from app import App, AppException
+from tools import load_yaml, md_to_html
 
 
 class WebApplication(tornado.web.Application):
@@ -69,14 +70,16 @@ class LoginHandler(BaseHandler):
     def get(self):
         self.render('login.html', error='')
 
-    # @gen.coroutine
-    def post(self):
+    async def post(self):
         uid = self.get_body_argument('uid')
         if uid.startswith('l'):  # remove prefix 'l'
             uid = uid[1:]
         pw = self.get_body_argument('pw')
 
-        if self.testapp.login(uid, pw):
+        loop = asyncio.get_event_loop()
+        login_ok = await loop.run_in_executor(None, self.testapp.login, uid, pw)
+
+        if login_ok:
             self.set_secure_cookie("user", str(uid), expires_days=30)
             self.redirect(self.get_argument("next", "/"))
         else:
@@ -206,7 +209,7 @@ class TestHandler(BaseHandler):
 
     # POST
     @tornado.web.authenticated
-    def post(self):
+    async def post(self):
         uid = self.current_user
 
         # self.request.arguments = {'answered-0': [b'on'], '0': [b'13.45']}
@@ -229,7 +232,9 @@ class TestHandler(BaseHandler):
                                    'numeric-interval'):
                     ans[i] = ans[i][0]
 
-        self.testapp.correct_test(uid, ans)
+        loop = asyncio.get_event_loop()
+        await loop.run_in_executor(None, self.testapp.correct_test, uid, ans)
+
         self.testapp.logout(uid)
         self.clear_cookie('user')
 
--
libgit2 0.21.2