Oct 08, 2026 by Offer

Load balancer: Answer Guide 2027

A load balancer distributes incoming traffic across multiple servers so no single machine is overwhelmed — improving reliability, since failed servers get routed around, and scalability, since capacity grows by adding servers. In a load balancer interview, explain the core job (spread requests, health-check backends), then name the common algorithms: round robin, least connections, and IP hash.

What This Tests in a Load balancer interview Question

Whether you understand the two purposes: availability (route around failures) and scalability (spread load).
Whether you know the standard algorithms and when each fits.
Whether you grasp the layer distinction: L4 (TCP) versus L7 (HTTP) balancing and why it matters.

How to Answer a Load balancer interview Question

Define it: sits in front of server pools, forwards each request to a healthy backend, rechecks health continuously.
Name the algorithms: round robin for even capacity, least connections for uneven request costs, IP hash for session affinity.
Add the L4/L7 nuance: L4 balances TCP connections fast; L7 understands HTTP and can route by URL or header.

Example phrasing: "A load balancer spreads requests across healthy servers and routes around failures. I would use round robin for uniform backends or least connections for variable-cost requests, and L7 balancing when routing decisions need HTTP awareness like URL-based rules."

Common Mistakes in a Load balancer interview Question

Describing it as only a performance tool and missing the availability story.
Not knowing any balancing algorithm by name.
Ignoring health checks — without them, the balancer keeps sending traffic to dead servers.

Load balancers sit at the center of every scalability discussion, so this question is really a gateway to system design. Answer it crisply with algorithms and health checks, and interviewers will trust you with the harder architecture questions ahead.

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FAQ

What is a load balancer in a load balancer interview?

A component that distributes incoming traffic across multiple servers and routes around unhealthy ones.

What are common load balancing algorithms?

Round robin, least connections, and IP hash — chosen based on backend uniformity and session needs.

What is the difference between L4 and L7 load balancing?

L4 balances at the TCP level; L7 understands HTTP and can route on URLs, headers, or cookies.

How does a load balancer detect failed servers?

Through health checks — periodic probes — removing backends that stop responding until they recover.

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