diff --git a/trans/managers.py b/trans/managers.py
index f8bdbf13f..9bba61d19 100644
--- a/trans/managers.py
+++ b/trans/managers.py
@@ -2,7 +2,7 @@ from django.db import models
 
 from lang.models import Language
 
-from util import is_plural, split_plural, join_plural
+from util import is_plural, split_plural, join_plural, msg_checksum
 
 class TranslationManager(models.Manager):
     def update_from_blob(self, subproject, code, path, blob):
@@ -23,16 +23,17 @@ class UnitManager(models.Manager):
         '''
         src = join_plural(unit.source.strings)
         ctx = unit.getcontext()
+        checksum = msg_checksum(src, ctx)
         import trans.models
         try:
             dbunit = self.get(
                 translation = translation,
-                source = src,
-                context = ctx)
+                checksum = checksum)
             force = False
         except:
             dbunit = trans.models.Unit(
                 translation = translation,
+                checksum = checksum,
                 source = src,
                 context = ctx)
             force = True
diff --git a/trans/models.py b/trans/models.py
index a95c5d236..4e6be47f5 100644
--- a/trans/models.py
+++ b/trans/models.py
@@ -164,8 +164,8 @@ class SubProject(models.Model):
 class Translation(models.Model):
     subproject = models.ForeignKey(SubProject)
     language = models.ForeignKey(Language)
-    translated = models.FloatField(default = 0)
-    fuzzy = models.FloatField(default = 0)
+    translated = models.FloatField(default = 0, db_index = True)
+    fuzzy = models.FloatField(default = 0, db_index = True)
     revision = models.CharField(max_length = 40, default = '', blank = True)
     filename = models.CharField(max_length = 200)
 
@@ -221,13 +221,14 @@ class Translation(models.Model):
 
 class Unit(models.Model):
     translation = models.ForeignKey(Translation)
+    checksum = models.CharField(max_length = 40, default = '', blank = True, db_index = True)
     location = models.TextField(default = '', blank = True)
     context = models.TextField(default = '', blank = True)
     flags = models.TextField(default = '', blank = True)
     source = models.TextField()
     target = models.TextField(default = '', blank = True)
-    fuzzy = models.BooleanField(default = False)
-    translated = models.BooleanField(default = False)
+    fuzzy = models.BooleanField(default = False, db_index = True)
+    translated = models.BooleanField(default = False, db_index = True)
 
     objects = UnitManager()
 
diff --git a/trans/util.py b/trans/util.py
index fd928a1ad..ca56767a0 100644
--- a/trans/util.py
+++ b/trans/util.py
@@ -1,3 +1,4 @@
+import hashlib
 
 PLURAL_SEPARATOR = '\x00\x00'
 
@@ -13,3 +14,14 @@ def split_plural(s):
 def join_plural(s):
     return PLURAL_SEPARATOR.join(s)
 
+def msg_checksum(source, context):
+    '''
+    Returns checksum of source string, used for quick lookup.
+
+    We use MD5 as it is faster than SHA1.
+    '''
+    m = hashlib.md5()
+    m.update(source)
+    m.update(context)
+    return m.hexdigest()
+