Features

cross-zone disabled by default

NLB provides a network interface in each AZ backed by a static IP. This static IP can be used to configure AZ specific DNS records.

NLB forwards the requests to the same AZ target in which it receives the request. This is useful to maintain AZ affinity and reduce costs due to cross AZ traffic.

NLB is a layer-4 device, works on layer-4 protocols, and is inherently sticky. Applications should close connections to not overload a single server behind NLB.

Ref Multi AZ architectures