diff --git a/.gitignore b/.gitignore
index 3e80c5b..92c5d4c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -105,3 +105,5 @@ venv.bak/
 
 # configuration
 rt2zammad.json
+# cache
+rt2zammad.cache
diff --git a/migrate.py b/migrate.py
index 0227fc3..11d98cc 100755
--- a/migrate.py
+++ b/migrate.py
@@ -3,13 +3,15 @@
 Quick and dirty attempt to migrate issues from Request Tracker to Zammad.
 """
 
+import pickle
 import json
 import os
 import sys
 
 from requests.exceptions import HTTPError
 from zammad_py import ZammadAPI
-from rt import Rt
+from zammad_py.api import TagList
+from rt import Rt, ALL_QUEUES
 
 TEMPLATE = """{
 "zammad_host": "",
@@ -43,3 +45,42 @@ source = Rt(config['rt_url'], config['rt_user'], config['rt_pass'])
 if not source.login():
     print('Failed to login to RT!')
     sys.exit(2)
+
+if os.path.exists('rt2zammad.cache'):
+    with open('rt2zammad.cache', 'rb') as handle:
+        data = pickle.load(handle)
+    users = data['users']
+    queues = data['queues']
+    tickets = data['tickets']
+
+else:
+    users = {}
+    tickets = []
+    queues = set()
+
+    def ensure_user(username):
+        if username not in users:
+            users[username] = source.get_user(username)
+
+
+    for i in range(1, 1000):
+        print('Loading ticket {}'.format(i))
+        ticket = source.get_ticket(i)
+        if ticket is None:
+            break
+        queues.add(ticket['Queue'])
+        ensure_user(ticket['Creator'])
+        ensure_user(ticket['Owner'])
+        history = source.get_history(i)
+        attachments = []
+        for a in source.get_attachments_ids(i):
+            attachment = source.get_attachment(i, a)
+            attachments.append(attachments)
+            ensure_user(attachment['Creator'])
+        tickets.append({
+            'ticket': ticket,
+            'history': history,
+            'attachments': attachments,
+        })
+    with open('rt2zammad.cache', 'wb') as handle:
+        data = pickle.dump({'users': users, 'queues': queues, 'tickets': tickets}, handle)