At Sinatra, what is the difference between a production environment and a development environment?

Basically, only templates depend on env var.

You can implement all other logical methods of the application based on the current env:

  if settings.production?
    # this will only run in production
  else
    # every other env
  end

You can also do something similar if conditional configurations are needed:

configure :production, :development do
  enable :logging
end