Here is the use case:
I am using Java (with Spring)
Once the user (through a web-app) confirms to the subscription, I want to send him an email exactly after 30 mins.
Now how to do this? Do I need a message broker? or something like ScheduledExecutorService?
Do I need some sort of queue?
Please advise.
Can look into quartz scheduler for this.
By the way a common strategy is to send a bulk of all pending mails in bulk in every 30 minutes or so. Quartz can help in do that as well.