Slow UI update for deleted events

I've built an integration that continuously syncs events between an external scheduling system and Exchange Online using Microsoft Graph.

I'm observing a recurring issue when deleting calendar events via Graph:

• A DELETE request to Graph returns success (204 No Content).
• A subsequent GET /events/{id} returns 404, confirming the event is deleted server-side.
• However, the event continues to appear in the Outlook UI (both Outlook Web and desktop) for an extended period (sometimes hours), even after page reloads or app restarts.

The odd behaviour

• The event is still displayed in the user interface for up to several hours
• The event persist through page reloads
• If the user clicks the event it opens briefly and immediately closes, the event disappears from the UI afterward.

Additional details

• Delete endpoint:

  /users/{id}/events/{id}

• Graph response:

  204 No Content

• Verified deletion via GET → 404
• Reproduces in both Outlook Web and Outlook desktop

Questions

• Is this a known Outlook client caching or calendar view indexing issue?
• Is there a way to force client reconciliation after deletes?
• Are there Graph or Exchange constraints around rapid create/update/delete cycles that could cause this UI inconsistency?