Your load balancer distributes traffic to prevent any server from being a SPOF. But what if the load balancer itself fails?
Active-Passive: Two load balancers. One handles traffic, one waits. If active fails, passive takes over using IP failover.
Active-Active: Both load balancers handle traffic. DNS returns both IPs. If one fails, DNS stops returning it.
Cloud providers handle this for you. AWS ELB, Google Cloud Load Balancing, and Azure Load Balancer are all available by default.
In interviews, mention that you'd use multiple load balancers to avoid SPOF.