diff --git a/CHANGELOG.rdoc b/CHANGELOG.rdoc
index 5823de5..c97f3d6 100644
--- a/CHANGELOG.rdoc
+++ b/CHANGELOG.rdoc
@@ -4,6 +4,7 @@ KalibroProcessor is the processing web service for Mezuro.
 
 == Unreleased
 
+* Optimize database structure by adding foreign keys and indexes where needed
 * Introduce performance tests for Aggregator
 * Update KolektiMetricfu
 
diff --git a/db/migrate/20160715192850_clean_inconsistencies.rb b/db/migrate/20160715192850_clean_inconsistencies.rb
new file mode 100644
index 0000000..3a63eed
--- /dev/null
+++ b/db/migrate/20160715192850_clean_inconsistencies.rb
@@ -0,0 +1,71 @@
+class CleanInconsistencies < ActiveRecord::Migration
+  def self.up
+    # Unset project reference for repositories with non-existing projects
+    execute <<-SQL
+      UPDATE repositories AS r
+      SET project_id = NULL
+      WHERE project_id = 0 OR NOT EXISTS (
+        SELECT 1 FROM projects AS p WHERE p.id = r.project_id
+      )
+    SQL
+
+    # Delete processings with non-existing repositories
+    execute <<-SQL
+      DELETE FROM processings AS p
+      WHERE NOT EXISTS(
+        SELECT 1 FROM repositories AS r WHERE r.id = p.repository_id
+      )
+    SQL
+
+    # Delete process times with non-existing processings
+    execute <<-SQL
+      DELETE FROM process_times AS t
+      WHERE NOT EXISTS (
+        SELECT 1 FROM processings AS p WHERE p.id = t.processing_id
+      )
+    SQL
+
+    # Delete module results with non-existing processings
+    execute <<-SQL
+      DELETE FROM module_results AS m
+      WHERE NOT EXISTS (
+        SELECT 1 FROM processings AS p WHERE p.id = m.processing_id
+      )
+    SQL
+
+    # Delete kalibro modules with non-existing module results
+    execute <<-SQL
+      DELETE FROM kalibro_modules AS k
+      WHERE NOT EXISTS (
+        SELECT 1 FROM module_results AS m WHERE m.id = k.module_result_id
+      )
+    SQL
+
+    # Delete metric results with non-existing module results
+    execute <<-SQL
+      DELETE FROM metric_results AS met
+      WHERE NOT EXISTS (
+        SELECT 1 FROM module_results AS mod WHERE mod.id = met.module_result_id
+      )
+    SQL
+
+    # Delete duplicate metric_results. Group them by (module_result, metric_configuration),
+    # then delete all but the one with the highest ID
+    # The double wrapping on the inner query is necessary because window functions
+    # cannot be used in WHERE in PostgreSQL.
+    execute <<-SQL
+      DELETE FROM metric_results
+      WHERE id IN (
+        SELECT t.id FROM (
+          SELECT id, ROW_NUMBER() OVER (PARTITION BY module_result_id, metric_configuration_id ORDER BY id DESC) AS rnum
+          FROM metric_results
+        ) AS t
+        WHERE t.rnum > 1
+      )
+    SQL
+  end
+
+  def self.down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end
diff --git a/db/migrate/20160715192900_add_indexes_to_kalibro_modules.rb b/db/migrate/20160715192900_add_indexes_to_kalibro_modules.rb
new file mode 100644
index 0000000..718ddd4
--- /dev/null
+++ b/db/migrate/20160715192900_add_indexes_to_kalibro_modules.rb
@@ -0,0 +1,6 @@
+class AddIndexesToKalibroModules < ActiveRecord::Migration
+  def change
+    add_foreign_key :kalibro_modules, :module_results, on_delete: :cascade
+    add_index :kalibro_modules, [:long_name, :granularity]
+  end
+end
diff --git a/db/migrate/20160715192901_add_indexes_to_module_results.rb b/db/migrate/20160715192901_add_indexes_to_module_results.rb
new file mode 100644
index 0000000..2726718
--- /dev/null
+++ b/db/migrate/20160715192901_add_indexes_to_module_results.rb
@@ -0,0 +1,6 @@
+class AddIndexesToModuleResults < ActiveRecord::Migration
+  def change
+    add_foreign_key :module_results, :module_results, column: 'parent_id'
+    add_foreign_key :module_results, :processings, on_delete: :cascade
+  end
+end
diff --git a/db/migrate/20160715192902_add_indexes_to_metric_results.rb b/db/migrate/20160715192902_add_indexes_to_metric_results.rb
new file mode 100644
index 0000000..86c61a8
--- /dev/null
+++ b/db/migrate/20160715192902_add_indexes_to_metric_results.rb
@@ -0,0 +1,8 @@
+class AddIndexesToMetricResults < ActiveRecord::Migration
+  def change
+    add_foreign_key :metric_results, :module_results, on_delete: :cascade
+    add_index :metric_results, :type
+    add_index :metric_results, [:module_result_id, :metric_configuration_id],
+              unique: true, name: 'metric_results_module_res_metric_cfg_uniq_idx'
+  end
+end
diff --git a/db/migrate/20160715192903_add_indexes_to_processings.rb b/db/migrate/20160715192903_add_indexes_to_processings.rb
new file mode 100644
index 0000000..a0d1ebc
--- /dev/null
+++ b/db/migrate/20160715192903_add_indexes_to_processings.rb
@@ -0,0 +1,6 @@
+class AddIndexesToProcessings < ActiveRecord::Migration
+  def change
+    add_foreign_key :processings, :repositories
+    add_foreign_key :processings, :module_results, column: 'root_module_result_id'
+  end
+end
diff --git a/db/migrate/20160715192904_add_indexes_to_process_times.rb b/db/migrate/20160715192904_add_indexes_to_process_times.rb
new file mode 100644
index 0000000..1639f4b
--- /dev/null
+++ b/db/migrate/20160715192904_add_indexes_to_process_times.rb
@@ -0,0 +1,5 @@
+class AddIndexesToProcessTimes < ActiveRecord::Migration
+  def change
+    add_foreign_key :process_times, :processings, on_delete: :cascade
+  end
+end
diff --git a/db/migrate/20160715192905_add_indexes_to_repositories.rb b/db/migrate/20160715192905_add_indexes_to_repositories.rb
new file mode 100644
index 0000000..dcf6b8d
--- /dev/null
+++ b/db/migrate/20160715192905_add_indexes_to_repositories.rb
@@ -0,0 +1,5 @@
+class AddIndexesToRepositories < ActiveRecord::Migration
+  def change
+    add_foreign_key :repositories, :projects
+  end
+end
diff --git a/db/migrate/20160716000521_remove_timestamps_from_module_results.rb b/db/migrate/20160716000521_remove_timestamps_from_module_results.rb
new file mode 100644
index 0000000..eadb25b
--- /dev/null
+++ b/db/migrate/20160716000521_remove_timestamps_from_module_results.rb
@@ -0,0 +1,6 @@
+class RemoveTimestampsFromModuleResults < ActiveRecord::Migration
+  def change
+    remove_column :module_results, :created_at, :string
+    remove_column :module_results, :updated_at, :string
+  end
+end
diff --git a/db/migrate/20160716000528_remove_timestamps_from_metric_results.rb b/db/migrate/20160716000528_remove_timestamps_from_metric_results.rb
new file mode 100644
index 0000000..4401fa0
--- /dev/null
+++ b/db/migrate/20160716000528_remove_timestamps_from_metric_results.rb
@@ -0,0 +1,6 @@
+class RemoveTimestampsFromMetricResults < ActiveRecord::Migration
+  def change
+    remove_column :metric_results, :created_at, :string
+    remove_column :metric_results, :updated_at, :string
+  end
+end
diff --git a/db/migrate/20160716000530_remove_timestamps_from_kalibro_modules.rb b/db/migrate/20160716000530_remove_timestamps_from_kalibro_modules.rb
new file mode 100644
index 0000000..e7d2abe
--- /dev/null
+++ b/db/migrate/20160716000530_remove_timestamps_from_kalibro_modules.rb
@@ -0,0 +1,6 @@
+class RemoveTimestampsFromKalibroModules < ActiveRecord::Migration
+  def change
+    remove_column :kalibro_modules, :created_at, :string
+    remove_column :kalibro_modules, :updated_at, :string
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index f576490..03aa5aa 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20151002172231) do
+ActiveRecord::Schema.define(version: 20160716000530) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -33,33 +33,31 @@
   add_index "delayed_jobs", ["priority", "run_at"], name: "delayed_jobs_priority", using: :btree
 
   create_table "kalibro_modules", force: :cascade do |t|
-    t.string   "long_name",        limit: 255
-    t.string   "granularity",      limit: 255
-    t.datetime "created_at"
-    t.datetime "updated_at"
-    t.integer  "module_result_id"
+    t.string  "long_name",        limit: 255
+    t.string  "granularity",      limit: 255
+    t.integer "module_result_id"
   end
 
+  add_index "kalibro_modules", ["long_name", "granularity"], name: "index_kalibro_modules_on_long_name_and_granularity", using: :btree
+
   create_table "metric_results", force: :cascade do |t|
-    t.integer  "module_result_id"
-    t.integer  "metric_configuration_id"
-    t.float    "value"
-    t.datetime "created_at"
-    t.datetime "updated_at"
-    t.string   "type",                              default: "MetricResult", null: false
-    t.integer  "line_number"
-    t.text     "message"
-    t.integer  "related_hotspot_metric_results_id"
+    t.integer "module_result_id"
+    t.integer "metric_configuration_id"
+    t.float   "value"
+    t.string  "type",                              default: "MetricResult", null: false
+    t.integer "line_number"
+    t.text    "message"
+    t.integer "related_hotspot_metric_results_id"
   end
 
+  add_index "metric_results", ["module_result_id", "metric_configuration_id"], name: "metric_results_module_res_metric_cfg_uniq_idx", unique: true, using: :btree
   add_index "metric_results", ["related_hotspot_metric_results_id"], name: "index_metric_results_on_related_hotspot_metric_results_id", using: :btree
+  add_index "metric_results", ["type"], name: "index_metric_results_on_type", using: :btree
 
   create_table "module_results", force: :cascade do |t|
-    t.float    "grade"
-    t.integer  "parent_id"
-    t.datetime "created_at"
-    t.datetime "updated_at"
-    t.integer  "processing_id"
+    t.float   "grade"
+    t.integer "parent_id"
+    t.integer "processing_id"
   end
 
   add_index "module_results", ["parent_id"], name: "index_module_results_on_parent_id", using: :btree
@@ -106,5 +104,13 @@
     t.string   "branch",                               default: "master", null: false
   end
 
+  add_foreign_key "kalibro_modules", "module_results"
+  add_foreign_key "metric_results", "module_results"
   add_foreign_key "metric_results", "related_hotspot_metric_results", column: "related_hotspot_metric_results_id"
+  add_foreign_key "module_results", "module_results", column: "parent_id"
+  add_foreign_key "module_results", "processings"
+  add_foreign_key "process_times", "processings"
+  add_foreign_key "processings", "module_results", column: "root_module_result_id"
+  add_foreign_key "processings", "repositories"
+  add_foreign_key "repositories", "projects"
 end