Practice load balancer vocabulary: Layer 4 vs Layer 7, balancing algorithms, health checks, sticky sessions, and AWS ALB configuration.
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What is the key difference between a Layer 4 and a Layer 7 load balancer?
A Layer 4 LB routes based on network-level info (IP, TCP port). A Layer 7 LB inspects HTTP content — headers, paths, cookies — enabling path-based routing, A/B traffic splits, etc.
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'The ___ check is failing for 2 of 5 instances.' Which noun fits?
'Health check' is the standard term for the periodic probe a load balancer uses to verify each backend instance is alive and ready to serve traffic.
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What are 'sticky sessions' in load balancer configuration?
Sticky sessions (also called session persistence or session affinity) ensure a user's requests always go to the same backend — important for stateful applications that store session data in memory.
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In 'round-robin vs. least-connections' load balancing, what is least-connections?
Least-connections routing sends new requests to the backend with the fewest current active connections — better than round-robin when request processing times vary significantly.
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'We use AWS ALB with ___ target groups.' Which adjective describes split-traffic routing?
AWS ALB supports 'weighted target groups' — you can direct, say, 90% of traffic to the stable version and 10% to a canary, enabling gradual rollouts and A/B testing.