Remove specific HTTP headers from Rack response.
In your config.ru:
# remove 'X-Request-Id', 'X-Runtime' and X-Rack-Cache headers
use Rack::HeaderFilter, ['X-Request-Id', 'X-Runtime', 'X-Rack-Cache']
In your application.rb:
# remove 'X-Request-Id', 'X-Runtime' and X-Rack-Cache headers
config.middleware.insert 0, 'Rack::HeaderFilter', ['X-Request-Id', 'X-Runtime', 'X-Rack-Cache']