concern_vs_service_object.rb

# Concern:
module Searchable
  extend ActiveSupport::Concern

  included do
    include Elasticsearch::Model
    scope :searchable, -> { where(searchable: true) }
  end

  module ClassMethods
    def search
      # …
    end
  end
end

#Service class:
class Indexer
  def initialize(model)
  end

  def index
    # …
  end
end