How fast should a personalization decision be?
Fast enough that ranking does not delay the page. Set a hard timeout and show a useful default when the decision misses it.
Use the smallest rule that works
Start with a useful default. Change it only when a fresh signal is strong enough to improve the decision. Keep inventory and availability as hard constraints, then measure conversion, profit, and returns against a control.
What to check before launch
Write down the rule, its data inputs, the fallback, and the condition that turns it off. Review small segments carefully. A dramatic result from a few sessions is not evidence.
Bottom line
Fast enough that ranking does not delay the page. Set a hard timeout and show a useful default when the decision misses it. Test the result against a control before expanding it.
Source: FTC, Bringing Dark Patterns to Light. Reviewed Sep 22, 2026.