I'm also struggling with this sporadic issue since many months. Actually i also had this already with resque.
My lucky guess is: the job gets triggered as the user registers and the user model is just saved. But the Sidekiq job already tries to load the user, which should be in the database, but maybe the db-transaction where the user.save
happened, doesn't seem to be commited yet.
So when i try to reproduce this issue, there IS an user with the given id, and maybe thats why you don't have any timestamp set in deleted_at
.
I will try to run the welcome-mailer with a slight delay of 5-10sec and check if this still happens.
Kind regards