Where or how does Sidekiq/Redis store an object when a Job is retrying?

We provide our Clients a way to preview mass emails being delivered to their Users. For some of the emails, we mock (OpenStruct) some objects and use them in the email view:

UserMailer:class UserMailer < ApplicationMailer

 def about_to_expire_card_reminder    ...    if params[:email_preview]      @subject += " (email de prueba)"      @user_default_credit_card = mock_credit_card    end    send_email(subject: @subject)  end  def mock_credit_card    OpenStruct.new(last_four_digits: "1234 (tarjeta de prueba)",                   expiration_date: 10.days.from_now.to_date)  endend

We were forcing errors today and noticed that the OpenStruct that mock_credit_card returns does not show up in the Sidekiq admin page where the retrying Job shows.

Retrying Job info:

Next Retry: in 3 minutesRetry Count: 4Queue: mailersJob: ActionMailer::MailDeliveryJobArguments: "UserMailer", "about_to_expire_card_reminder", "deliver_now", {"params"=>{"user"=>{"_aj_globalid"=>"gid://database/User/1"}, "to"=>info@testemail.com", "email_preview"=>true, "aj_symbol_keys"=>["user,"to","email_preview"]}, "args"=>[],"_aj_symbol_keys"=>["params","args"]}Error: ActionView::Template:Error: undefined method "last_four_digits" for #struct expiration_date="2021-03-31">

Where does Sidekiq store the mocked OpenStruct object? Is it serialized? Does it take up memory until the job is finished or dropped?

Any insights would be appreciated. Let me know if you need more code.