could not serialize access due to read/write dependencies among transactions

Q: How do I prevent "could not serialize access due to read/write dependencies among transactions — 40001"?

- Build retry-on-40001 into the data-access layer once, so every SERIALIZABLE transaction is automatically replayed on a serialization failure. Treat it as expected, not exceptional. - Keep SERIALIZABLE transactions small and fast; never hold one open across user/network think-time. - Access tables and rows in a consistent order across all code paths to minimize dangerous structures. - For known h

Incident Brief

What happened: A transaction running under SERIALIZABLE isolation is rolled back – usually at COMMIT – even though every statement in it was valid and no constraint was violated:

ERROR: 40001: could not serialize access due to read/write dependencies among transactions
DETAIL: Reason code: Canceled on identific

Immediate action: 1. Read the HINT – "The transaction might succeed if retried." That is the supported remedy.
2. Roll back the aborted transaction (it is already aborted; issue ROLLBACK to end it cleanly).
3. Re-run t

The fix

Copy-paste · works on PG 14–18

Read the HINT - "The transaction might succeed if retried." That is the supported remedy.
Roll back the aborted transaction (it is already aborted; issue ROLLBACK to end it cleanly).
Re-run the ENTIRE transaction from the beginning. Replaying only the failed statement is wrong - the snapshot is gone.
Wrap the transaction in a bounded retry loop with exponential backoff + jitter, catching SQLSTATE 40001 (and 40P01 deadlock_detected, which is handled the same way). On a fresh attempt t

Reproduce & verify

What you see

A transaction running under SERIALIZABLE isolation is rolled back - usually at COMMIT - even though every statement in it was valid and no constraint was violated:

ERROR:  40001: could not serialize access due to read/write dependencies among transactions
DETAIL:  Reason code: Canceled on identific

Confirm it yourself

Confirm it really is SSI (read/write dependency) and not the REPEATABLE READ "concurrent update" variant.

-- 1) What isolation level is the failing transaction using? It must be SERIALIZABLE for THIS message:
SHOW default_transaction_isolation;
-- inside the transaction:
SELECT current_setting('transaction_isolation');

-- 2) Reproduce deterministically with two sessions, A and B, on a small table:
--    (session A)            (session B)
--    BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE;
--

Same result on 14 · 15 · 16 · 17 · 18 — identical message on every version.

Prevent it everywhere

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Free — what you just got

The copy-paste fix
Why it happens
Reproduced on real PostgreSQL
No fleet-wide audit
No prevention tooling

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`serialization_failure` could not serialize access due to read/write dependencies among transactions — 40001