Didn't love this all that much, but perhaps it'll get useful again some day...

config_initializers_locale.rb

require 'i18n/backend/active_record'

# https://github.com/svenfuchs/i18n-active_record

if Translation.table_exists?
  # Translation = I18n::Backend::ActiveRecord::Translation # Breaks Ransack :-(
  I18n.backend = I18n::Backend::ActiveRecord.new
  I18n::Backend::ActiveRecord.send(:include, I18n::Backend::Memoize)
  I18n::Backend::Simple.send(:include, I18n::Backend::Memoize)
  I18n::Backend::Simple.send(:include, I18n::Backend::Pluralization)
  I18n.backend = I18n::Backend::Chain.new(I18n::Backend::Simple.new, I18n.backend)
end

# Try to emulate GNU gettext usage model

def _(translation_key, interpolations = {})
  locale = I18n.locale
  begin
    value = I18n.translate!(translation_key, interpolations, raise: true)
  rescue
    if t = Translation.find_by(key: translation_key, locale: locale)
      t.update_attribute(:value, translation_key) if default? t
    else
      t = Translation.new(key: translation_key, interpolations: interpolations, locale: locale)
      t.value = translation_key if default? t
      t.save
    end
    value = t.value || translation_key
  end
  return value
end

def default?(t)
  I18n.locale == :en && t.value.blank?
end