Tagged trading
2 pieces
- · 11 min read
Model the Trade, Not the Screens
When quote, acceptance and settlement exist as three screens calling services ad hoc, the acceptance and the trade record can disagree, and a double tap can execute twice. An explicit state machine with defined transitions makes the impossible combination unrepresentable rather than merely unlikely. An append-only record of transitions lets settlement and reporting be projections of one history instead of two copies that drift apart.
- · 10 min read
Positions, Not Stock Levels: What Changes When the Operator Is the Counterparty
An operator who buys and sells on their own book is not an intermediary moving other people's goods. What they hold is exposure, and exposure is not a quantity. A warehouse model tracking units in and units out loses the exposure view entirely, and turns a reallocation into an untraceable edit to two numbers. Modelling positions explicitly, with allocation and reallocation recorded as transitions, lets the book explain itself.