HMS does not guarantee that each notification has unique IDs.
SENTRY-1803 solved the issue with Sentry to handle those duplicated events IDs. However, HMS notifications with duplicated events IDs could appear late on the HMS side due to delay issues on the DB (especially on HMS HA mode). These events could not be fetched by Sentry if we already processed a duplicated event ID before.
1. HMS 1 attempts to persist event ID = 1
2. HMS 2 attempts to persist event ID = 1
3. HMS 1 commits event ID = 1
4. Sentry fetches notifications >= 1 (bringing the event from HMS 1)
5. HMS 2 commits event ID = 1
6. Sentry fetches notifications >= 2 (no events are fetched)
HMS 2 event ID = 1 is never fetched nor processed by Sentry.
The above scenario could cause Sentry to be out-of-sync because of these events that were not committed on time.