diff --git a/swh/scheduler/celery_backend/runner.py b/swh/scheduler/celery_backend/runner.py
index 67738c3..9d48c74 100644
--- a/swh/scheduler/celery_backend/runner.py
+++ b/swh/scheduler/celery_backend/runner.py
@@ -1,62 +1,84 @@
-# Copyright (C) 2015  The Software Heritage developers
+# Copyright (C) 2015-2017 The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
+import time
+
 import arrow
 from celery import group
 
 from ..backend import SchedulerBackend
 from .config import app as main_app
 
 
+# Max batch size for tasks
+MAX_NUM_TASKS = 10000
+
+
 def run_ready_tasks(backend, app):
     """Run all tasks that are ready"""
 
-    backend_names = {}
-
     while True:
+        throttled = False
         cursor = backend.cursor()
-        pending_tasks = backend.grab_ready_tasks(num_tasks=10000,
-                                                 cursor=cursor)
+        task_types = {}
+        pending_tasks = []
+        for task_type in backend.get_task_types(cursor=cursor):
+            task_type_name = task_type['type']
+            task_types[task_type_name] = task_type
+            max_queue_length = task_type['max_queue_length']
+            if max_queue_length:
+                backend_name = task_type['backend_name']
+                queue_name = app.tasks[backend_name].task_queue
+                queue_length = app.get_queue_length(queue_name)
+                num_tasks = min(max_queue_length - queue_length,
+                                MAX_NUM_TASKS)
+            else:
+                num_tasks = MAX_NUM_TASKS
+            if num_tasks > 0:
+                pending_tasks.extend(
+                    backend.grab_ready_tasks(task_type_name,
+                                             num_tasks=num_tasks,
+                                             cursor=cursor))
+
         if not pending_tasks:
             break
 
         celery_tasks = []
         for task in pending_tasks:
-            backend_name = backend_names.get(task['type'])
-            if not backend_name:
-                task_type = backend.get_task_type(task['type'], cursor=cursor)
-                backend_names[task['type']] = task_type['backend_name']
-                backend_name = task_type['backend_name']
-
             args = task['arguments']['args']
             kwargs = task['arguments']['kwargs']
 
-            celery_task = app.tasks[backend_name].s(*args, **kwargs)
+            celery_task = app.tasks[
+                task_types[task['type']]['backend_name']
+            ].s(*args, **kwargs)
 
             celery_tasks.append(celery_task)
 
         group_result = group(celery_tasks).delay()
 
         backend_tasks = [{
             'task': task['id'],
             'backend_id': group_result.results[i].id,
             'scheduled': arrow.utcnow(),
         } for i, task in enumerate(pending_tasks)]
 
         backend.mass_schedule_task_runs(backend_tasks, cursor=cursor)
 
         backend.commit()
 
+        if throttled:
+            time.sleep(10)
+
 
 if __name__ == '__main__':
     for module in main_app.conf.CELERY_IMPORTS:
         __import__(module)
 
     main_backend = SchedulerBackend()
     try:
         run_ready_tasks(main_backend, main_app)
     except:
         main_backend.rollback()
         raise