Interview Questions/Phone Screen/Types of Load Balancers
IntermediatePhone
2 min

Types of Load Balancers

Load BalancingNetworkingInfrastructure
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Interview Question

Explain the difference between Layer 4 and Layer 7 load balancing. Provide examples of when each would be used.

Key Points to Cover
  • L4: routes traffic based on IP/port (TCP/UDP)
  • L7: routes based on content (HTTP headers, paths)
  • L4 example: NLB; L7 example: ALB, NGINX
Evaluation Rubric
Explains Layer 4 correctly30% weight
Explains Layer 7 correctly30% weight
Gives real-world examples40% weight
Hints
  • 💡Think OSI model layers.
Common Pitfalls to Avoid
  • ⚠️Confusing the OSI layers or misattributing functionalities (e.g., saying L4 does SSL termination).
  • ⚠️Failing to provide concrete use-case examples, only listing technologies.
  • ⚠️Not explaining the 'why' behind using one over the other (e.g., L4 for performance, L7 for intelligent routing).
  • ⚠️Overlooking the trade-offs involved (L4's speed vs. L7's feature set).
  • ⚠️Focusing too heavily on a single vendor's product names without explaining the general concept.
Potential Follow-up Questions
  • Which is better for microservices?
  • How does SSL termination work?
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