diff --git a/Gemfile b/Gemfile
index 64d62a3..2eb052d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -6,6 +6,12 @@ gem "rails", "4.0.2"
 # Use mysql2 as the database for Active Record
 gem "mysql2", ">= 0.3.14"
 
+# Use PostgreSQL as the database for Active Record
+# gem "pg"
+#
+# NOTE: If you use PostgreSQL, you must still leave enabled the above mysql2 gem
+#       for Sphinx full text search to function.
+
 # Use Rails3-style mass assignment security
 gem "protected_attributes"
 
diff --git a/app/models/keystore.rb b/app/models/keystore.rb
index 123e8da..8f9caf5 100644
--- a/app/models/keystore.rb
+++ b/app/models/keystore.rb
@@ -1,21 +1,29 @@
 class Keystore < ActiveRecord::Base
-  validates_presence_of :key
+  self.primary_key = "key"
 
-  attr_accessible nil
+  validates_presence_of :key
 
   def self.get(key)
     self.where(:key => key).first
   end
 
+  def self.value_for(key)
+    self.where(:key => key).first.try(:value)
+  end
+
   def self.put(key, value)
     if Keystore.connection.adapter_name == "SQLite"
       Keystore.connection.execute("INSERT OR REPLACE INTO " <<
         "#{Keystore.table_name} (`key`, `value`) VALUES " <<
         "(#{q(key)}, #{q(value)})")
-    else
+    elsif Keystore.connection.adapter_name =~ /Mysql/
       Keystore.connection.execute("INSERT INTO #{Keystore.table_name} (" +
         "`key`, `value`) VALUES (#{q(key)}, #{q(value)}) ON DUPLICATE KEY " +
         "UPDATE `value` = #{q(value)}")
+    else
+      kv = self.find_or_create_key_for_update(key, value)
+      kv.value = value
+      kv.save!
     end
 
     true
@@ -26,8 +34,6 @@ class Keystore < ActiveRecord::Base
   end
 
   def self.incremented_value_for(key, amount = 1)
-    new_value = nil
-
     Keystore.transaction do
       if Keystore.connection.adapter_name == "SQLite"
         Keystore.connection.execute("INSERT OR IGNORE INTO " <<
@@ -35,16 +41,36 @@ class Keystore < ActiveRecord::Base
           "(#{q(key)}, 0)")
         Keystore.connection.execute("UPDATE #{Keystore.table_name} " <<
           "SET `value` = `value` + #{q(amount)} WHERE `key` = #{q(key)}")
-      else
+      elsif Keystore.connection.adapter_name =~ /Mysql/
         Keystore.connection.execute("INSERT INTO #{Keystore.table_name} (" +
           "`key`, `value`) VALUES (#{q(key)}, #{q(amount)}) ON DUPLICATE KEY " +
           "UPDATE `value` = `value` + #{q(amount)}")
+      else
+        kv = self.find_or_create_key_for_update(key, 0)
+        kv.value = kv.value.to_i + amount
+        kv.save!
+        return kv.value
       end
 
-      new_value = self.value_for(key)
+      self.value_for(key)
     end
+  end
 
-    return new_value
+  def self.find_or_create_key_for_update(key, init = nil)
+    loop do
+      kv = self.lock(true).where(:key => key).first
+      return kv if kv
+
+      begin
+        self.create! do |kv|
+          kv.key = key
+          kv.value = init
+          kv.save!
+        end
+      rescue ActiveRecord::RecordNotUnique
+        nil
+      end
+    end
   end
 
   def self.decrement_value_for(key, amount = -1)
@@ -54,8 +80,4 @@ class Keystore < ActiveRecord::Base
   def self.decremented_value_for(key, amount = -1)
     self.incremented_value_for(key, amount)
   end
-
-  def self.value_for(key)
-    self.get(key).try(:value)
-  end
 end
diff --git a/db/migrate/20120816203248_keystore_bigint.rb b/db/migrate/20120816203248_keystore_bigint.rb
index f3c1d31..4348762 100644
--- a/db/migrate/20120816203248_keystore_bigint.rb
+++ b/db/migrate/20120816203248_keystore_bigint.rb
@@ -1,6 +1,6 @@
 class KeystoreBigint < ActiveRecord::Migration
   def up
-    execute("ALTER TABLE keystores CHANGE value value BIGINT")
+    change_column :keystores, :value, :integer, :limit => 8
   end
 
   def down
diff --git a/db/migrate/20130526164230_change_tables_to_utf8mb4.rb b/db/migrate/20130526164230_change_tables_to_utf8mb4.rb
index fb30235..6728b3e 100644
--- a/db/migrate/20130526164230_change_tables_to_utf8mb4.rb
+++ b/db/migrate/20130526164230_change_tables_to_utf8mb4.rb
@@ -1,5 +1,7 @@
 class ChangeTablesToUtf8mb4 < ActiveRecord::Migration
   def up
+    return if connection.adapter_name !~ /Mysql/
+
     [ "comments", "invitations", "messages", "moderations", "stories", "users" ].each do |t|
       execute("alter table #{t} convert to character set utf8mb4")
     end