We recently upgraded our HubSpot instance to hs-2021 and immediately started experiencing critical issues with our lead data sync process. Leads are being duplicated across multiple records, and our sync job is failing intermittently with API timeout errors.
The deduplication logic that worked perfectly in our previous version now seems completely broken. We’re also seeing integration mapping errors where custom lead properties aren’t being transferred correctly. Here’s what we’re seeing in the logs:
POST /contacts/v1/contact/batch
Error 429: Rate limit exceeded
Duplicate contact detected: email@example.com
Our sync job configuration hasn’t changed, but something in hs-2021 is causing these failures. Has anyone else encountered this after upgrading? We need to resolve this urgently as it’s affecting our sales team’s ability to work with accurate lead data.
Yes, there’s a critical change in hs-2021. The deduplication now happens at the property level, not just email. You need to ensure your custom lead properties are mapped correctly in the integration hub. Check your property mappings - if they’re not explicitly defined, HubSpot won’t recognize them as duplicate identifiers. Also, verify that your sync job is using the v3 Contacts API instead of v1, as v1 has deprecated deduplication features in hs-2021.
I’ve seen similar issues after upgrading to hs-2021. The API rate limits were adjusted in this version, and the default deduplication settings changed. Check your sync job’s batch size - you might be hitting the new rate limits faster than before.
I encountered this exact scenario last month. The integration mapping configuration needs to be updated for hs-2021. The system now requires explicit property-level deduplication rules. Navigate to Settings > Integrations > Integration Hub and verify that your lead sync integration has the correct property mappings defined. Make sure each custom property has a corresponding HubSpot property mapped, and that the deduplication strategy is set at the integration level, not just in individual API calls.
Here’s the complete solution that addresses all three focus areas - deduplication logic, sync job configuration, and integration mapping:
1. Deduplication Logic Fix:
In hs-2021, you must explicitly define deduplication criteria in your API requests. Update your contact creation calls to include the deduplication strategy:
POST /crm/v3/objects/contacts
Content-Type: application/json
{
"properties": {"email": "lead@example.com"},
"idProperty": "email"
}
2. Sync Job Configuration:
Adjust your sync job settings to accommodate hs-2021’s stricter rate limits:
- Reduce batch size from 100 to 40 contacts per request
- Implement 2-second delays between batches
- Add exponential backoff for 429 errors (start with 5s, double each retry, max 60s)
- Enable the ‘Skip Duplicates’ option in your sync job settings
3. Integration Mapping:
The critical issue is in your Integration Hub configuration. Navigate to Settings > Integrations > [Your Integration] > Field Mappings. For each custom lead property, you need to:
- Map source field to exact HubSpot property (case-sensitive)
- Set ‘Deduplication Priority’ to ‘High’ for email and unique identifiers
- Enable ‘Bidirectional Sync’ if you need updates to flow both ways
- Add ‘Last Modified Date’ to mapping to prevent overwriting newer data
After making these changes, run a test sync with a small batch (10-20 records) to verify deduplication works correctly. Monitor the API logs for any remaining 429 errors. If you still see duplicates, check that your source system isn’t sending multiple records with the same email within the same batch - HubSpot processes batch requests simultaneously, which can create race conditions.
One final critical point: Clear your integration cache before running the full sync. Go to Settings > Integrations > [Your Integration] > Advanced > Clear Cache. This ensures hs-2021 picks up your new deduplication rules immediately.
This comprehensive approach has resolved the issue for three clients I’ve worked with post-hs-2021 upgrade.
The 429 error is definitely a rate limiting issue. In hs-2021, HubSpot reduced the batch contact creation limit from 100 to 50 contacts per request. You’ll need to adjust your sync job configuration to use smaller batches and implement exponential backoff. Also, the deduplication logic now requires explicit email matching parameters in your API calls. Without these, HubSpot creates new contacts instead of updating existing ones. Check if your integration mapping includes the ‘dedupeStrategy’ parameter set to ‘email’ in your POST requests.
Thanks for the insights. I’ve reduced the batch size to 40 contacts per request, but we’re still seeing duplicate records being created. The deduplication logic seems to be ignoring our email matching criteria entirely. Is there a specific API endpoint or parameter that changed in hs-2021 for handling duplicates?