When 2 or more workers are modifying the same row, it is possible to encounter 13535. The time of the begin transaction and the modification are the defining properties. When the transaction begin time is before the latest row modification, error 13535 is encountered.
T1 starts a transaction
T1 is context switched or client has not submitted the modification request
T2 starts a transaction, just after T1
T2 updates the row in the table
T1 attempts to update row and is blocked by T2 or T2 commits transaction before T1 issues the modification
T2 commits the transaction
T1