1) I don't think I've actually used has_and_belongs_to_many since 2008. Generally, most people seem to use has_many :through, which is somewhat clearer and allo

1) I don't think I've actually used has_and_belongs_to_many since 2008. Generally, most people seem to use has_many :through, which is somewhat clearer and allows more complex join models. 2) All that has_many :through does is simplify the syntax of accessing objects through many-to-many join tables. If you know how to use many-to-many joins, has_many :through is just a simpler syntax that enables you to explicitly mention the join table only once, and have it used implicitly thereafter. Nothing all that complicated about that, and there's nothing that needs to be "kept in sync" any more than it would if you were doing pure SQL. 3) find_by_* methods are hardly complicated. Have a read through the source of ActiveRecord::Base's method_missing and you should get the idea of how they work pretty quickly. Give yourself half an hour, because it is pretty tight code that does a lot and does it efficiently, but it's not difficult to follow if you know ruby: if match = DynamicFinderMatch.match(method_id) attribute_names = match.attribute_names super unless all_attributes_exists?(attribute_names) if match.finder? options = arguments.extract_options! relation = options.any? ? construct_finder_arel(options, current_scoped_methods) : scoped relation.send :find_by_attributes, match, attribute_names, *arguments elsif match.instantiator? scoped.send :find_or_instantiator_by_attributes, match, attribute_names, *arguments, &block end From: http://github.com/rails/rails/blob/master/activerecord/lib/active_record/base.rb http://github.com/rails/rails/blob/master/activerecord/lib/a...