It is the minimum lead time between "now" and the earliest time a customer may choose for a Real Time order. The default is 5 minutes.

Effects:

• On the ordering page the customer sees the error "Please select a future time window for your order" if the chosen time is earlier than now + buffer.
• When the system suggests a default time, it starts at now + buffer and snaps to the next open window.
• At checkout the time is re-validated: it must be at least now + buffer and inside one of the day's windows (the windows themselves are also shifted by the buffer when checked). If the saved time is no longer valid the system silently moves it to the next valid time; if none exists, checkout is blocked.

Use a bigger buffer if your kitchen needs more prep time before the first order can be promised.