What is the best way to notify users that document expired in database?

Question

In my application users create documents which are then saved in the database. The document has expireAt field which is set to 30 days ahead from the date it is created. After the expiration date the document is considered as inactive.

So, what I want is to send an email to the user after expiration date to notify him that his document is now inactive. The only solution I see is to create a cron job and periodically poll the database for expired documents.

But I'm not sure if periodical polling is a good approach and would like to know if there are other ways of doing this.

P.S. The app is built with nodejs + mongoDB

Answer 1

Tykaty, you can try to use 2 features of mongodb:

• Expire data https://docs.mongodb.com/manual/tutorial/expire-data/
• Change events https://docs.mongodb.com/manual/reference/change-events/ https://docs.mongodb.com/manual/changeStreams/#watch-a-collection--database--or-deployment

The idea is simple. You store the documents as before. Add a collection that you will watch and add there objects which should expire, link each document in your original collection to a corresponding object to be expired(1 to 1 link). When the object is deleted by mongo engine(expired), you get a notification with it's _id. Find this _id in your original collection of documents to understand which doc was expired. Here you are.

Of course, you can start with polling, final solution depends on the data and it's usage, the load as well.