Maglev is a network load balancer that operates at L3/L4. ECMP on the upstream routers spreads traffic for a VIP across a pool of Maglevs, but the Maglev itself

Maglev is a network load balancer that operates at L3/L4. ECMP on the upstream routers spreads traffic for a VIP across a pool of Maglevs, but the Maglev itself does more complicated backend selection. Envoy is an L7 proxy, so it's the moral equivalent of the Google GFE (which, conveniently enough, is the next layer of load balancing behind Maglev for most Google services).