Atomic Promotion Usage Limits

Context

Concurrent buyers can compete for the last permitted code use. Capacity must be acquired at the point the sale commits.

Decision

Placement conditionally acquires code and campaign capacity in stable campaign order and retains frozen redemption allocations within its transaction.

Alternatives Considered

Hold campaign capacity during every preview. Abandoned carts would retain scarce uses before a sale exists.

Increment counters after committing the order. Concurrent sales could exceed capacity before the later count update.

Consequences

Conditional counter updates serialize contested capacity. A refused acquisition prevents order placement from committing. Use counters do not advance the staff configuration version.