Backend Server Overview

Backend servers are the compute resources that receive and process traffic forwarded by a load balancer. They are the service endpoints behind a load balancer, while the load balancer acts as the traffic entry point and distributes requests to these servers.

Backend servers are usually elastic compute instances identified by private IP addresses. They typically reside in the same global VPC as the load balancer.

A load balancer becomes fully effective only after backend servers are configured and associated with its listeners.

Functions of Backend Servers

Backend servers perform the following core functions:

• Request Processing Handle client requests forwarded by the load balancer, such as web requests, API calls, or service connections.

• Service Hosting Run application components, including web services, databases, microservices, or middleware.

• Traffic Offloading Share incoming traffic load to prevent any single server from becoming a performance bottleneck.

• High Availability Support Work with load balancer health checks to ensure traffic is routed only to healthy servers.

Key Features

Flexible Backend Types

Backend servers can be configured using:

• Elastic compute instances

• Private IP addresses

Weighted Traffic Distribution

Each backend server can be assigned a weight to control how much traffic it receives relative to others.

Health Check Integration

Load balancers continuously monitor backend server health:

• Unhealthy servers are automatically removed from traffic distribution

• Recovered servers are automatically reinstated

Real Client IP Preservation

In supported forwarding modes (such as Destination NAT), backend servers can obtain the real client source IP for logging, auditing, and security analysis.