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+---
+title: Keep Transactions Short to Reduce Lock Contention
+impact: MEDIUM-HIGH
+impactDescription: 3-5x throughput improvement, fewer deadlocks
+tags: transactions, locking, contention, performance
+---
+
+## Keep Transactions Short to Reduce Lock Contention
+
+Long-running transactions hold locks that block other queries. Keep transactions as short as possible.
+
+**Incorrect (long transaction with external calls):**
+
+```sql
+begin;
+select * from orders where id = 1 for update;  -- Lock acquired
+
+-- Application makes HTTP call to payment API (2-5 seconds)
+-- Other queries on this row are blocked!
+
+update orders set status = 'paid' where id = 1;
+commit;  -- Lock held for entire duration
+```
+
+**Correct (minimal transaction scope):**
+
+```sql
+-- Validate data and call APIs outside transaction
+-- Application: response = await paymentAPI.charge(...)
+
+-- Only hold lock for the actual update
+begin;
+update orders
+set status = 'paid', payment_id = $1
+where id = $2 and status = 'pending'
+returning *;
+commit;  -- Lock held for milliseconds
+```
+
+Use `statement_timeout` to prevent runaway transactions:
+
+```sql
+-- Abort queries running longer than 30 seconds
+set statement_timeout = '30s';
+
+-- Or per-session
+set local statement_timeout = '5s';
+```
+
+Reference: [Transaction Management](https://www.postgresql.org/docs/current/tutorial-transactions.html)