UNABLE_TO_LOCK_ROW

Salesforce could not get an exclusive lock on a record within about 10 seconds. The message reads unable to obtain exclusive access to this record.

Common causes

• Two transactions update the same record, or children of the same parent, at the same time.
• Bulk API parallel mode splits children of one parent across batches.
• Data skew: one account with more than 10,000 children, or one user owning a very large number of records.
• Roll-up summary fields and master-detail relationships lock the parent on every child save.
• Slow triggers or flows hold locks for a long time.
• Scheduled jobs overlap with integrations or each other.

How to fix

• Sort load files by parent ID so each parent’s children land in the same batch.
• Use serial mode in Bulk API, or reduce the batch size.
• Reschedule jobs so they do not run at the same time.
• Add retry logic to integrations. A retry a few seconds later usually succeeds.
• Reduce skew by spreading children across more parents or owners.
• Shorten transactions by removing unnecessary automation from the object.