diff --git a/lib/attr_json/attribute_definition/registry.rb b/lib/attr_json/attribute_definition/registry.rb
index 2fb9220..8657fc3 100644
--- a/lib/attr_json/attribute_definition/registry.rb
+++ b/lib/attr_json/attribute_definition/registry.rb
@@ -26,6 +26,8 @@ def initialize(hash = {})
         @name_to_definition = hash.dup
         @store_key_to_definition = {}
         definitions.each { |d| store_key_index!(d) }
+
+        @container_attributes_registered = Hash.new { Set.new }
       end
 
       def fetch(key, *args, &block)
@@ -73,6 +75,32 @@ def with(*definitions)
         end
       end
 
+
+      # We need to lazily set the container type only the FIRST time
+      #
+      # While also avoiding this triggering ActiveRecord to actually go to DB,
+      # we don't want DB connection forced on boot, that's a problem for many apps,
+      # including that may not have a DB connection in initial development.
+      # (#type_for_attribute forces DB connection)
+      #
+      # AND we need to call container attriubte on SUB-CLASS AGAIN, iff sub-class
+      # has any of it's own new registrations, to make sure we get the right type in
+      # sub-class!
+      #
+      # So we just keep track of whether we've registered ourselves, so we can
+      # first time we need to.
+      #
+      # While current implementation is simple, this has ended up a bit fragile,
+      # a different API that doesn't require us to do this implicitly lazily
+      # might be preferred! But this is what we got for now.
+      def register_container_attribute(attribute_name:, model:)
+        @container_attributes_registered[attribute_name.to_sym] << model
+      end
+
+      def container_attribute_registered?(attribute_name:, model:)
+         @container_attributes_registered[attribute_name.to_sym].include?(model)
+      end
+
       protected
 
       def add!(definition)
diff --git a/lib/attr_json/record.rb b/lib/attr_json/record.rb
index 745675f..904358e 100644
--- a/lib/attr_json/record.rb
+++ b/lib/attr_json/record.rb
@@ -160,22 +160,14 @@ def attr_json(name, type, **options)
         options.assert_valid_keys(AttributeDefinition::VALID_OPTIONS + [:validate, :accepts_nested_attributes])
         container_attribute = options[:container_attribute]
 
-        # TODO arg check container_attribute make sure it exists. Hard cause
-        # schema isn't loaded yet when class def is loaded. Maybe not.
 
-        # Want to lazily add an attribute cover to the json container attribute,
-        # only if it hasn't already been done. WARNING we are using internal
-        # Rails API here, but only way to do this lazily, which I thought was
-        # worth it. On the other hand, I think .attribute is idempotent, maybe we don't need it...
-        #
-        # We set default to empty hash, because that 'tricks' AR into knowing any
-        # application of defaults is a change that needs to be saved.
-        unless attributes_to_define_after_schema_loads[container_attribute.to_s] &&
-               attributes_to_define_after_schema_loads[container_attribute.to_s].first.is_a?(AttrJson::Type::ContainerAttribute) &&
-               attributes_to_define_after_schema_loads[container_attribute.to_s].first.model == self
-           # If this is already defined, but was for superclass, we need to define it again for
-           # this class.
+        # Make sure to "lazily" register attribute for *container* class if this is the first time
+        # this container attribute hsa been encountered for this specific class. The registry
+        # helps us keep track. Kinda messy, in future we may want a more explicit API
+        # that does not require us to implicitly track first-time per-container.
+        unless self.attr_json_registry.container_attribute_registered?(model: self, attribute_name: container_attribute.to_sym)
            attribute container_attribute.to_sym, AttrJson::Type::ContainerAttribute.new(self, container_attribute), default: -> { {} }
+           self.attr_json_registry.register_container_attribute(model: self, attribute_name: container_attribute.to_sym)
         end
 
         self.attr_json_registry = attr_json_registry.with(