I'd venture in guessing that the biggest cost is the team salary, and not the DigitalOcean and Algolia bills. How do you cover for that?

Don't you have problems with email delivery being delayed (mostly because of anti-spam throttling on the receiver's end)?

Great! But how do you transfer the link to the user? If you transfer the link by email, how do you manage a possible delay before the email reaches the user's mailbox?