Calendar sync creates duplicate events after integrating event management with Microsoft Exchange

CRM Adobe Experience Cloud
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1

We recently integrated our Adobe Experience Cloud event management module with Microsoft Exchange for calendar synchronization. The integration works, but we’re seeing duplicate events appearing in user calendars after the sync runs.

The issue seems related to how event UIDs are being mapped between systems. When an event is updated in AEC (like changing the time or adding attendees), the sync creates a new calendar entry instead of updating the existing one. We’re also having problems with recurring events - each instance gets duplicated.

Here’s what we’re seeing in the sync logs:


Event UID: AEC-EVT-12345
Exchange UID: 040000008200E00074C5B7101A82E00800000000B0
Status: Created new entry (expected: update)

This is causing major confusion for our sales team who use these calendars daily. Has anyone dealt with event UID mapping and recurrence rule handling in AEC-Exchange integrations? We need a proper deduplication strategy.

2

Have you implemented any kind of sync state tracking? Without maintaining a record of what’s already been synced and when, your integration will keep creating duplicates. I’d recommend adding a custom field in AEC to store the Exchange calendar item ID, and always check for its existence before deciding whether to create or update. The sync logs you posted show it’s always choosing ‘create’ - that’s your smoking gun right there.

3

Another thing to watch for is timezone handling between the systems. If the timestamps don’t match exactly due to timezone conversion issues, your deduplication logic might fail to recognize that two events are actually the same. Exchange is very particular about ISO 8601 format with proper timezone offsets. Make sure you’re converting AEC timestamps correctly before comparison. I’ve debugged similar issues where events were considered different purely because one had ‘Z’ suffix and the other had ‘+00:00’ - technically the same time but string comparison failed. Use proper datetime comparison, not string matching.

4

Thanks for all the insights. We do have timezone issues too - didn’t even think about that aspect. So it sounds like we need better UID mapping and proper recurrence handling. Are there any best practices for the mapping table structure?

5

I’ve seen this exact issue before. The problem is that Exchange generates its own UID format while AEC uses a different convention. When your sync process doesn’t maintain a proper mapping table between these UIDs, each update looks like a new event to Exchange. You need to store the Exchange UID that gets returned after the initial creation and use that for all subsequent updates to the same AEC event.

6

Let me provide a comprehensive solution addressing all three critical areas you’re struggling with.

Event UID Mapping Strategy: Implement a bidirectional mapping table in your integration layer. When creating an event in Exchange, store both UIDs:


Mapping Table:
AEC_Event_ID | Exchange_UID | Last_Modified | Content_Hash
AEC-EVT-12345 | 040000008200E... | 2025-03-20T10:00:00Z | a3f5e9...

Before any sync operation, query this table first. If a mapping exists, use PUT/PATCH to update the Exchange event rather than POST to create a new one.

Recurrence Rule Handling: The key is to sync the master recurring event, not individual instances. When AEC marks an event as recurring:

  1. Extract the recurrence pattern from AEC (daily, weekly, monthly, etc.)
  2. Convert it to Exchange RRULE format (RFC 5545 compliant)
  3. Send ONE calendar item with the RRULE property set
  4. For exceptions (cancelled instances or modified occurrences), handle those separately using Exchange’s exception mechanisms

Never sync recurring events as individual instances unless they’re true standalone events. Your current approach is likely iterating through occurrences and creating each one individually.

Deduplication Logic Implementation: Implement a three-tier deduplication check:

  1. Pre-sync validation: Before making any Exchange API call, check your mapping table for existing entries. If found, this is an update operation.

  2. Content hash comparison: Generate a hash of the event’s key properties (title, start time, end time, attendees, location). Compare against the stored hash. If identical, skip the sync entirely - no changes detected.

  3. Post-sync reconciliation: After syncing, query Exchange to verify only one event exists per AEC event. If duplicates are found, implement cleanup logic:


if (exchangeEventsCount > 1) {
  keepNewest = findEventByLastModified();
  deleteOlders();
  updateMappingTable(keepNewest.UID);
}

Additional Critical Fixes:

  • Timezone normalization: Convert all timestamps to UTC before comparison. Use proper datetime libraries, not string matching. Store timezone info separately if needed for display.

  • Concurrency handling: Implement optimistic locking using Exchange’s ChangeKey property. This prevents race conditions when multiple sync processes run simultaneously.

  • Error recovery: When sync fails midway, log the state. On retry, check completion status before re-attempting to avoid creating duplicates during error recovery.

  • Incremental sync: Only sync events modified since last successful sync. Use AEC’s lastModifiedDate and Exchange’s delta queries to minimize processing.

Implement these changes in phases: Start with the mapping table and UID tracking, then fix recurrence handling, and finally add the deduplication checks. Monitor your sync logs for ‘update’ vs ‘create’ operations - you should see mostly updates once the mapping is established. For your existing duplicates, run a one-time cleanup script that consolidates them based on matching AEC event IDs before going live with the new logic.