CODEWITHSUNDEEP
cqrsevent-sourcingsensitive-data
user3603308
user3603308

Reputation: 355

Logical deletion with event sourcing (potentially with sensitive data / GDPR)

I understand that event sources are supposed to be immutable and append only.

However, I'm wondering how I handle a logical delete. If the user clicks 'delete' on the UI and they are expecting a hard delete, do I include a IsDeleted flag on my event? Are there other options here?

Edit: The question has special interest when there is sensitive data around, maybe stored in the event itself, and the user expects it to be completely flashed-out from our systems. This can relate to the EU GDPR regulation and laws.

Upvotes: 4

Views: 1957

Answers (4)

Sandy
Sandy

Reputation: 1504

As @Vincent Hendriks said, "You could publish a 'deleted' event which would remove/ mark the data as deleted in your read database".

Here is a very good example that demonstrates this concept: http://next.belus.com/Demos/Events

In the demo, click the Edit link and press Delete button. At the bottom of the page, see the event that gets created.

Upvotes: 0

Vincent Hendriks
Vincent Hendriks

Reputation: 86

You could publish a 'deleted' event which would remove/ mark the data as deleted in your read database, but this isn't a hard delete (which you specify in your question). You will still have the data in your event store.

Hard deletes are actually pretty difficult when using event sourcing. I assume you're working with event sourced customer data? There are usually a few solutions for this, but they aren't really pretty:

  • You either don't eventsource your sensitive customer data but store this seperately and just reference this from your aggregate in some way

  • You either delete old events (be aware that this might break more than you'd like, but it depends on your design / application)

  • You either add a deleted event and change existing events to strip out the sensitive data.

Upvotes: 4

Roman Eremin
Roman Eremin

Reputation: 1451

Usually you don't display events in your UI, you display your read model that is calculated from events.

For instance, you can have events

TASK_CREATED "one"

TASK_CREATED "two"

TASK_CREATED "three"

TASK_DELETED "two"

In your read model (list of tasks) update code you just add items on TASK_CREATED event and remove it on TASK_DELETED event, so resulting list would be:

"one"

"three"

So, if user clicks 'delete' in the UI, it sends DELETE_TASK command to the aggregate, aggregate publishes TASK_DELETED event, and this event is applied to the read model (removing item from the list). Now when you query the read model, it will have one item removed.

Upvotes: 0

VoiceOfUnreason
VoiceOfUnreason

Reputation: 57279

do I include a IsDeleted flag on my event? Are there other options here?

If you are asking "Can I undo an event, by setting the isDeleted flag?"; no, that's not usually how we do it. Instead, we append a new event that "reverses" the effect of the first. You'll sometimes see this described as a compensating event. In mature domains (think accounting), there is often an explicit protocol for reversing events.

Upvotes: 0

Related Questions