Entity delete validation in a microservice environment

Question

In a microservice environment there are two services: Service A and Service B.

Service A manages an entity called x which has one to many relationship with service B's entity called y

When a network request hits to Service A to delete a specific x, Service A makes an internal network request to service B to validate whether specific x being used with any y item.

In a microservice environment, is there a better and more efficient way to handle this kind of request and validation among two services?

Also these options already came to table, however not optimal.

1. Managing a cache on Service A about y isn't viable.
2. Managing a key/property on each x about whether it's being used or not, was also considered. However there's a development overhead of migrating all the old data with new property.
3. Let the front-end (webapp) directly calls Service B's validation before hitting to delete. However there's a possibility to have a false positive with the timing.

Answer 1

If Peter's approach is not viable for you, an alternative:

• Mark service A's x as DeletePending
• Send message to service B
• Service B checks its ys and either:
  • acknowledges with a DeleteApproved message or
  • refuses with a DeleteRefused message
• Service A receives a message:
  • DeleteApproved --> delete the object
  • DeleteRejected --> set x back to Alive status

BTW: if you have such a tight coupling between services, check your boundaries. Probably A and B should not be separate services in the first place.

Answer 2

Is the following scenario viable for you?

• Mark Service A's x entity as SoftDeleting / NotReachable / name it...
  • This should prevent to create new y entities in Service B, so Service B has to check x before allowing creation of y
  • Send a notification about from Service A about x status change
• Process Service A's status change event in Service B
  • Mark all y entities as SoftDeleted / Inactive / name it...
  • Send a notification from Service B about x related records status change
• Process Service B's status change event in Service A
  • Mark Service A;s x entity as SoftDeleted* / Inactive / name it...

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BTW: Sam Newman's Monolith 2 Microservices book has a dedicated chapter about database migration. Some part of it discussing this topic and fortunately it is available online for free.