Transaction states

What it is

Explicit states distinguish pending, successful, failed, and unknown outcomes.

When to use it

Represent financial lifecycle and allowed transitions.

Syntax

pending -> settled | failed
unknown -> settled | failed (after confirmation)

Example

UPDATE transactions SET status = 'settled'
WHERE id = ? AND status = 'pending';
-- Check exactly one row changed and record the transition atomically.

Common mistakes

A timeout does not prove failure; enums alone do not enforce transitions.

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