diff --git a/flatisfy/database/__init__.py b/flatisfy/database/__init__.py
index d6780fd..82e6c33 100644
--- a/flatisfy/database/__init__.py
+++ b/flatisfy/database/__init__.py
@@ -13,7 +13,12 @@ from sqlalchemy.engine import Engine
 from sqlalchemy.orm import sessionmaker
 from sqlalchemy.exc import OperationalError, SQLAlchemyError
 
+# Import models
+import flatisfy.models.postal_code  # noqa: F401
+import flatisfy.models.public_transport  # noqa: F401
 import flatisfy.models.flat  # noqa: F401
+import flatisfy.models.constraint  # noqa: F401
+
 from flatisfy.database.base import BASE
 from flatisfy.database.whooshalchemy import IndexService
 
diff --git a/flatisfy/models/constraint.py b/flatisfy/models/constraint.py
index 75e1df6..d421f3d 100644
--- a/flatisfy/models/constraint.py
+++ b/flatisfy/models/constraint.py
@@ -7,8 +7,9 @@ from __future__ import absolute_import, print_function, unicode_literals
 
 import logging
 from sqlalchemy import (
-    Column, Float, Integer, String
+    Column, Float, ForeignKey, Integer, String, Table
 )
+from sqlalchemy.orm import relationship
 from sqlalchemy_utils.types.json import JSONType
 from sqlalchemy_utils.types.scalar_list import ScalarListType
 
@@ -42,6 +43,13 @@ class PostTypes(enum.Enum):
     SHARING = 2
 
 
+association_table = Table(
+    'constraint_postal_codes_association', BASE.metadata,
+    Column('constraint_id', Integer, ForeignKey('constraints.id')),
+    Column('postal_code_id', Integer, ForeignKey('postal_codes.id'))
+)
+
+
 class Constraint(BASE):
     """
     SQLAlchemy ORM model to store a search constraint.
@@ -52,18 +60,28 @@ class Constraint(BASE):
     name = Column(String)
     type = Column(EnumListType(PostTypes, int))
     house_types = Column(EnumListType(HouseTypes, int))
-    postal_codes = Column(ScalarListType())  # TODO
+    # TODO: What happens when one delete a postal code?
+    postal_codes = relationship("PostalCode", secondary=association_table)
+
     area_min = Column(Float, default=None)  # in m^2
     area_max = Column(Float, default=None)  # in m^2
+
     cost_min = Column(Float, default=None)  # in currency unit
     cost_max = Column(Float, default=None)  # in currency unit
+
     rooms_min = Column(Integer, default=None)
     rooms_max = Column(Integer, default=None)
+
     bedrooms_min = Column(Integer, default=None)
     bedrooms_max = Column(Integer, default=None)
+
     minimum_nb_photos = Column(Integer, default=None)
     description_should_contain = Column(ScalarListType())  # list of terms
-    time_to = Column(JSONType)  # TODO
+
+    # Dict mapping names to {"gps": [lat, lng], "time": (min, max) }
+    # ``min`` and ``max`` are in seconds and can be ``null``.
+    # TODO: Use an additional time_to_places table?
+    time_to = Column(JSONType)
 
     def __repr__(self):
         return "<Constraint(id=%s, name=%s)>" % (self.id, self.name)
diff --git a/flatisfy/models/flat.py b/flatisfy/models/flat.py
index 6fece03..1627444 100644
--- a/flatisfy/models/flat.py
+++ b/flatisfy/models/flat.py
@@ -8,12 +8,11 @@ from __future__ import absolute_import, print_function, unicode_literals
 import logging
 import enum
 
-import arrow
-
 from sqlalchemy import (
-    Column, Enum, Float, SmallInteger, String, Text, inspect
+    Column, Enum, Float, ForeignKey, Integer, SmallInteger, String, Table,
+    Text, inspect
 )
-from sqlalchemy.orm import validates
+from sqlalchemy.orm import relationship, validates
 from sqlalchemy_utils.types.arrow import ArrowType
 from sqlalchemy_utils.types.json import JSONType
 from sqlalchemy_utils.types.scalar_list import ScalarListType
@@ -55,6 +54,14 @@ AUTOMATED_STATUSES = [
     FlatStatus.ignored
 ]
 
+stations_association_table = Table(
+    'stations_flats_association', BASE.metadata,
+    Column(
+        'public_transport_id', Integer, ForeignKey('public_transports.id')
+    ),
+    Column('flat_id', Integer, ForeignKey('flats.id'))
+)
+
 
 class Flat(BASE):
     """
@@ -72,7 +79,7 @@ class Flat(BASE):
     cost = Column(Float)
     currency = Column(String)
     utilities = Column(Enum(FlatUtilities), default=FlatUtilities.unknown)
-    date = Column(ArrowDate)
+    date = Column(ArrowType)
     details = Column(JSONType)
     location = Column(String)
     phone = Column(String)
@@ -86,18 +93,27 @@ class Flat(BASE):
     notes = Column(Text)
     notation = Column(SmallInteger, default=0)
 
-    # Flatisfy data
-    # TODO: Should be in another table with relationships
-    flatisfy_stations = Column(JSONType)
-    flatisfy_postal_code = Column(String)
+    # Flatisfy found stations
+    # TODO: What happens when one deletes a station?
+    flatisfy_stations = relationship("PublicTransport",
+                                     secondary=stations_association_table)
+    # Flatisfy found postal code
+    # TODO: What happens when one deletes a postal code?
+    flatisfy_postal_code_id = Column(Integer, ForeignKey('postal_codes.id'))
+    flatisfy_postal_code = relationship("PostalCode")
+    # Computed time to
     flatisfy_time_to = Column(JSONType)
-    flatisfy_constraint = Column(String)
+    # Constraint relationship
+    # TODO: What happens when one deletes a constraint?
+    # TODO: A flat could match multiple constraints
+    flatisfy_constraint_id = Column(Integer, ForeignKey('constraints.id'))
+    flatisfy_constraint = relationship("Constraint")
 
     # Status
     status = Column(Enum(FlatStatus), default=FlatStatus.new)
 
     # Date for visit
-    visit_date = Column(ArrowDate)
+    visit_date = Column(ArrowType)
 
     @validates('utilities')
     def validate_utilities(self, _, utilities):