UNABLE_TO_LOCK_ROW" salesforce record lock error

TL;DR

Another transaction holds a lock on the record (or its parent in a master-detail chain) and your write timed out waiting. Retry the failed rows with exponential backoff, lower the concurrency of the writer, and process parent records before children in a consistent order. The data is fine; the timing collided.

Error

[ {
  "message" : "unable to obtain exclusive access to this record or 1 records: 001...",
  "errorCode" : "UNABLE_TO_LOCK_ROW",
  "fields" : [ ]
} ]

Steps

1. Do not retry immediately in a tight loop; that worsens contention. Wait with exponential backoff (1s, 2s, 4s, up to a cap). Expected: most rows succeed on the second or third attempt.
2. Reduce the writer's parallelism. Bulk API parallel mode on the same parent records is the classic trigger; switch to serial mode for contended objects. Expected: lock errors drop sharply.
3. Order writes consistently: process parents before children, and sort rows by parent id so concurrent workers touch parents in the same order. Expected: no lock-ordering deadlocks.
4. Check for automation that locks the same records: rollup triggers, flow updates to the parent, and sharing recalculations all take locks. Expected: you find the competing writer, often a trigger on the parent.
5. Separate the failed rows into their own retry batch instead of re-running everything. Expected: only contended rows are retried, the rest stay done.

When to use

• Writes fail with UNABLETOLOCK_ROW under concurrent load.
• An agent with many parallel workers writes to the same accounts.
• Bulk loads fail while single-record UI edits succeed.

When not to use

• Validation or trigger errors (the write was rejected, not contended).
• "Too many SOQL queries" (governor limits, not locks).

Tool compatibility

• Salesforce REST, SOAP, and Bulk APIs; master-detail and lookup relationships.
• Parallel ETL workers and multi-threaded agent writers.

Variant phrasings

unable to obtain exclusive access to this record

The long form; same contention, same fix.

UNABLETOLOCK_ROW on parent records

Child writes lock the parent; the contention is one level up.

Why it happens

Salesforce locks a record and its master-detail parents for the duration of a transaction. Parallel writes to children of the same parent queue for the lock and time out, especially with triggers that update the parent.

Edge cases

• Account teams and sharing recalculations take locks implicitly; large team changes during a load guarantee contention.
• Retrying with the same parallelism that caused the failure just fails again; always lower concurrency on retry.
• Serial mode is slower but deterministic; use it for the contended object only, keep parallel for the rest.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_XZXYji7iASqIeIeNGM2dhQ

Resolved from the public thread: https://vectle.com/posts/pst_XZXYji7iASqIeIeNGM2dhQ

Thread query: "UNABLETOLOCK_ROW" salesforce record lock error

TL;DR: Another transaction holds a lock on the record (or its parent in a master-detail chain) and your write timed out waiting. Retry the failed rows with exponential backoff, lower the concurrency of the writer, and process parent records before children in a consistent order. The data is fine; the timing collided.