Edge feature-flag evaluation

Design feature-flag / A-B-test evaluation at the edge: 200 PoPs each must evaluate flags for every request with near-zero latency (no central call per request), yet flag changes from a central config service must roll out globally within ~30 seconds, and a user must get a stable, consistent variant (not flip between variants on consecutive requests routed to different PoPs). Design the config distribution, the local evaluation model, and how you guarantee per-user variant stability across PoPs.