diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 01c1255437b5..ce6f83e5b3ae 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -11,6 +11,10 @@ This project adheres to `Semantic Versioning`_ starting with version 1.0.
 
 Added
 -----
+- automatic creation of index on the ``sender_id`` column when using an SQL
+  tracker store. If you have an existing data and you are running into performance
+  issues, please make sure to add an index manually using
+  ``CREATE INDEX event_idx_sender_id ON events (sender_id);``.
 
 Changed
 -------
diff --git a/rasa/core/tracker_store.py b/rasa/core/tracker_store.py
index 71d41673354f..101a62164ce4 100644
--- a/rasa/core/tracker_store.py
+++ b/rasa/core/tracker_store.py
@@ -274,7 +274,7 @@ class SQLEvent(Base):
         __tablename__ = "events"
 
         id = Column(Integer, primary_key=True)
-        sender_id = Column(String, nullable=False)
+        sender_id = Column(String, nullable=False, index=True)
         type_name = Column(String, nullable=False)
         timestamp = Column(Float)
         intent_name = Column(String)