Load Balancer
A system that spreads incoming traffic across multiple servers so no single server gets overwhelmed.
Think of it like
Like a host at a restaurant entrance directing each new party to whichever table's server has the lightest load.
Junior or senior?
Junior sounds like
Hasn't thought about what happens to user sessions once traffic is spread across servers.
Senior sounds like
Can explain exactly how they handled it.
Ask them
“How did your app handle user sessions once traffic was spread across multiple servers behind a load balancer?”
Sounds like real experience
Describes a specific session-handling decision — sticky sessions, moving session state to Redis, a health-check misconfiguration that caused an outage — not just that a load balancer existed.
Probe further if
Describes a load balancer as something the infrastructure team set up, with no account of a session, health-check, or traffic-distribution problem they personally dealt with.