An execution in LUSID, also known as “fills”, reflects the quantity of an order placement a broker has been able to fulfill. LUSID can receive an execution in any shape, but the two core components received are:
The quantity filled.
The price each instrument unit was filled at (typically an average price is given for the entire quantity filled).
One placement might be filled over several executions, meaning that the total quantity ordered is accepted and completed by a broker in several chunks.
For example, as a Trader you might have placed an order block with a broker to buy 250 AAPL US equity shares. The broker might sell you 100 shares at once for an average price of $150; this is one execution. LUSID automatically updates with the execution, so at this point LUSID shows the placement as 40% filled. As more of the placement is executed, the fill rate in LUSID increases until it hits 100% (or meets the placement's time in force condition).
You can configure LUSID to decide what happens if a placement cannot be fully filled before meeting the time in force condition, such as by market close.