Load Balancing and Horizontal Scaling Questions

Covers principles and mechanisms for distributing traffic and scaling services horizontally. Includes load balancing algorithms such as round robin, least connections, and consistent hashing; health checks, connection draining, and sticky sessions; and session management strategies for stateless and stateful services. Explains when to scale horizontally versus vertically, capacity planning, and trade offs of each approach. Also includes infrastructure level autoscaling concepts such as auto scaling groups, launch templates, target tracking and step scaling policies, and how load balancers and autoscaling interact to absorb traffic spikes. Reviews different load balancer types and selection criteria, integration with service discovery, and operational concerns for maintaining availability and performance at scale.

MediumSystem Design

0 practiced

Design a blue-green deployment process that uses a load balancer to switch traffic with zero downtime. Describe routing updates, health verification steps, database migration concerns (if any), and rollback procedure. Assume the service is stateless HTTP but has background jobs that act on the same database.

MediumTechnical

0 practiced

You must support sticky sessions for a WebSocket-based product behind AWS ALB. Describe the options to provide session affinity, their trade-offs, and how to ensure new connections from a client go to the same backend even after scaling events. Include how to handle failover when the sticky backend fails.

MediumTechnical

0 practiced

Explain the benefits and drawbacks of cross-zone (or cross-availability-zone) load balancing. How does it affect latency, cost, and capacity utilization? When might you disable cross-zone balancing and what alternative would you implement to preserve availability?

EasyTechnical

0 practiced

Describe the types of health checks a load balancer should support (e.g., TCP, HTTP(s)/gRPC probe, application-level heartbeat). Explain how you choose probe interval, timeout, and unhealthy/healthy thresholds for a service with average 200ms request latency and occasional 2s background jobs. Include trade-offs (false positives vs detection speed).

HardTechnical

0 practiced

Explain rendezvous (highest-random-weight) hashing and compare it to ring-based consistent hashing with virtual nodes. Analyze rebalancing cost, lookup complexity, and ease of implementation at scale. When is rendezvous hashing the better choice?

Unlock Full Question Bank

Get access to hundreds of Load Balancing and Horizontal Scaling interview questions and detailed answers.

Join thousands of developers preparing for their dream job.