diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 7839f7544b..8e958a851e 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Remove `cache_attributes` and friends. All attributes are cached.
+
+    *Sean Griffin*
+
 *   Remove deprecated method `ActiveRecord::Base.quoted_locking_column`.
 
     *Akshay Vishnoi*
diff --git a/activerecord/lib/active_record/attribute_methods/read.rb b/activerecord/lib/active_record/attribute_methods/read.rb
index a354cd7503..7b7e37884b 100644
--- a/activerecord/lib/active_record/attribute_methods/read.rb
+++ b/activerecord/lib/active_record/attribute_methods/read.rb
@@ -35,35 +35,22 @@ module ActiveRecord
 
       extend ActiveSupport::Concern
 
-      ATTRIBUTE_TYPES_CACHED_BY_DEFAULT = [:datetime, :time, :date]
-
-      included do
-        class_attribute :attribute_types_cached_by_default, instance_writer: false
-        self.attribute_types_cached_by_default = ATTRIBUTE_TYPES_CACHED_BY_DEFAULT
-      end
-
       module ClassMethods
-        # +cache_attributes+ allows you to declare which converted attribute
-        # values should be cached. Usually caching only pays off for attributes
-        # with expensive conversion methods, like time related columns (e.g.
-        # +created_at+, +updated_at+).
-        def cache_attributes(*attribute_names)
-          cached_attributes.merge attribute_names.map { |attr| attr.to_s }
-        end
-
-        # Returns the attributes which are cached. By default time related columns
-        # with datatype <tt>:datetime, :time, :date</tt> are cached.
-        def cached_attributes
-          @cached_attributes ||= columns.select { |c| cacheable_column?(c) }.map { |col| col.name }.to_set
-        end
-
-        # Returns +true+ if the provided attribute is being cached.
-        def cache_attribute?(attr_name)
-          cached_attributes.include?(attr_name)
+        [:cache_attributes, :cached_attributes, :cache_attribute?].each do |method_name|
+          define_method method_name do |*|
+            cached_attributes_deprecation_warning(method_name)
+            true
+          end
         end
 
         protected
 
+        def cached_attributes_deprecation_warning(method_name)
+          ActiveSupport::Deprecation.warn(<<-MESSAGE.strip_heredoc)
+            Calling `#{method_name}` is no longer necessary. All attributes are cached.
+          MESSAGE
+        end
+
         if Module.methods_transplantable?
           def define_method_attribute(name)
             method = ReaderMethodCache[name]
@@ -89,16 +76,6 @@ module ActiveRecord
             end
           end
         end
-
-        private
-
-        def cacheable_column?(column)
-          if attribute_types_cached_by_default == ATTRIBUTE_TYPES_CACHED_BY_DEFAULT
-            true
-          else
-            attribute_types_cached_by_default.include?(column.type)
-          end
-        end
       end
 
       # Returns the value of the attribute identified by <tt>attr_name</tt> after
@@ -122,11 +99,7 @@ module ActiveRecord
             return block_given? ? yield(name) : nil
           }
 
-          if self.class.cache_attribute?(name)
-            @attributes[name] = column.type_cast_from_database(value)
-          else
-            column.type_cast_from_database value
-          end
+          @attributes[name] = column.type_cast_from_database(value)
         }
       end
 
diff --git a/activerecord/test/cases/attribute_methods_test.rb b/activerecord/test/cases/attribute_methods_test.rb
index 139fe9c04b..a366caf875 100644
--- a/activerecord/test/cases/attribute_methods_test.rb
+++ b/activerecord/test/cases/attribute_methods_test.rb
@@ -517,43 +517,17 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     end
   end
 
-  def test_only_time_related_columns_are_meant_to_be_cached_by_default
-    expected = %w(datetime time date).sort
-    assert_equal expected, ActiveRecord::Base.attribute_types_cached_by_default.map(&:to_s).sort
-  end
+  def test_deprecated_cache_attributes
+    assert_deprecated do
+      Topic.cache_attributes :replies_count
+    end
 
-  def test_declaring_attributes_as_cached_adds_them_to_the_attributes_cached_by_default
-    default_attributes = Topic.cached_attributes
-    Topic.cache_attributes :replies_count
-    expected = default_attributes + ["replies_count"]
-    assert_equal expected.sort, Topic.cached_attributes.sort
-    Topic.instance_variable_set "@cached_attributes", nil
-  end
+    assert_deprecated do
+      Topic.cached_attributes
+    end
 
-  def test_cacheable_columns_are_actually_cached
-    assert_equal cached_columns.sort, Topic.cached_attributes.sort
-  end
-
-  def test_accessing_cached_attributes_caches_the_converted_values_and_nothing_else
-    t = topics(:first)
-    cache = t.instance_variable_get "@attributes"
-
-    assert_not_nil cache
-    assert cache.empty?
-
-    all_columns = Topic.columns.map(&:name)
-    uncached_columns = all_columns - cached_columns
-
-    all_columns.each do |attr_name|
-      attribute_gets_cached = Topic.cache_attribute?(attr_name)
-      val = t.send attr_name unless attr_name == "type"
-      if attribute_gets_cached
-        assert cached_columns.include?(attr_name)
-        assert_equal val, cache[attr_name]
-      else
-        assert uncached_columns.include?(attr_name)
-        assert !cache.include?(attr_name)
-      end
+    assert_deprecated do
+      Topic.cache_attribute? :replies_count
     end
   end