Speaker: David Seddon (TODO)
Slides: TODO
Video: TODO
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Cuncurrent workers can cause issues with things like balances:
- Worker 1 checks balance then removes funds
- Worker 2 checks balance then removes funds
- This can lead to double spending.
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Postgres's default isolation level is read commited.
- Writes wait if another transaction is already writing (this uses a readonly lock).
select_for_update()delays read until readonly locks are released.
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Select for update on customer account (not ledger) can prevent double spending (pessimistic locking.)