- 07 Oct, 2025
- 0 Comments
- 1 Min Read
ERROR: could not serialize access due to concurrent update
PostgreSQL Could Not Serialize Access Due to Concurrent Update – Explained
When multiple transactions try to modify the same data at the same time under the SERIALIZABLE or REPEATABLE READ isolation level, PostgreSQL prevents conflicts to maintain data consistency.
You’ll see this error:
ERROR: could not serialize access due to concurrent update
Why This Happens
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Two concurrent transactions are modifying the same row.
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Using
SERIALIZABLEorREPEATABLE READisolation level. -
Application retries or updates without checking locks.
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Long-running transactions holding row locks.
Fixes for PostgreSQL Could Not Serialize Access Due to Concurrent Update
1. Retry the Transaction Automatically
Serialization failures are transient — just retry the transaction:
BEGIN; -- your queries COMMIT; -- if fails, rollback and retry
2. Use a Lower Isolation Level (if safe)
Switch from SERIALIZABLE to READ COMMITTED:
3. Reduce Transaction Scope
Keep transactions short and specific to minimize lock contention.
4. Use FOR UPDATE Locks
Lock rows before updating:
SELECT * FROM table_name WHERE id = 1 FOR UPDATE;
This ensures only one transaction can modify that row at a time.
5. Detect Conflicts in Application Logic
Handle retry logic in your app (e.g., using retry loops in Python, Java, etc.).
Conclusion
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