What Is a Cloud Load Balancer?

A single server cannot safely handle traffic growth, failure, deployment changes, and public access at the same time.

Companies need load balancers to keep applications available, scale traffic, route requests, terminate HTTPS, and remove unhealthy servers automatically.

A load balancer is a traffic front door that accepts client requests and forwards them to healthy backend targets based on rules and health checks.

If you understand front door, backend pool, health check, routing rule, TLS termination, and failover, you can understand load balancers in AWS, Azure, Google Cloud, Kubernetes, Nginx, and enterprise networks.

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DNS points to a public load balancer. The load balancer terminates HTTPS, checks backend health, routes traffic to app servers in private subnets, and sends logs to observability storage.

Put the load balancer in front of multiple private backend targets instead of exposing each server directly.

This creates a stable public endpoint while allowing backend servers to scale, fail, update, or be replaced without changing the user-facing address.

Expose one VM directly; use DNS round-robin only; put public IPs on every app server; use one reverse proxy without redundancy.

A managed load balancer increases cost but reduces operational burden. A self-managed proxy gives control but requires HA, patching, monitoring, and capacity planning.

Backend compute can be VMs, containers, autoscaling groups, Kubernetes services, or serverless targets depending on platform design.

Load balancer sits in public subnet or managed edge layer, while backend targets usually stay in private subnets with restricted inbound rules.

Static assets should often go through CDN and object storage instead of passing all traffic through the application load balancer.

The load balancer should not expose databases directly. Databases remain private behind the application layer.

Use HTTPS, modern TLS policy, web firewall when needed, restricted backend security groups, header controls, and access logs.

Monitor request count, latency, HTTP status codes, target health, TLS errors, rejected connections, and backend saturation.

Use health checks, multiple targets, multiple zones, autoscaling integration, and safe deployment strategies.

Scale backend pools horizontally and keep the application stateless so any healthy instance can serve requests.

Allow backend traffic only from the load balancer, block direct public access to app servers, and log public requests.

Use CDN for cacheable content, avoid unnecessary cross-zone traffic when possible, and choose the correct load balancer type for workload needs.

When users see errors, check DNS, certificate, load balancer health, routing rules, target health, backend logs, and recent deployment changes.

Bad health check path, expired certificate, no healthy targets, wrong firewall rule, overloaded backend, wrong routing rule, and sticky session problems.

Confirm HTTPS works; confirm health checks are accurate; confirm at least two backend targets; confirm backend is not public; confirm access logs are enabled.

Rollback routing rule, renew certificate, remove bad target, scale backend, fix health check, or shift traffic to a healthy environment.

A SaaS company needs to deploy new app versions without downtime while keeping backend servers private.

Explain how a load balancer improves availability and why health checks can cause outages if configured incorrectly.

Draw a public load balancer with two private app servers in different zones. Define health check path, security rules, TLS certificate, and failure behavior.

High Availability; VPC; Autoscaling; CDN; Web Application Firewall