What is Load Balancer & How Load Balancing works?

A load balancer is a networking device or software application that distributes and balances the incoming traffic among the servers to provide high availability, efficient utilization of servers and high performance.

• Works as a "traffic cop" routing client requests across all servers
• Ensures that no single server bears too many requests, which helps improve the performance, reliability and availability of applications.
• Highly used in cloud computing domains, data centers and large-scale web applications where traffic flow needs to be managed.

Issues without Load Balancer?

Several problem will occur without the load balancer, these are:

• Single Point of Failure: If the server goes down or something happens to the server the whole application will be interrupted and it will become unavailable for the users for a certain period. It will create a bad experience for users which is unacceptable for service providers.
• Overloaded Servers: There will be a limitation on the number of requests that a web server can handle. If the business grows and the number of requests increases the server will be overloaded.
• Limited Scalability: Without a load balancer, adding more servers to share the traffic is complicated. All requests are stuck with one server and adding new servers won’t automatically solve the load issue.

Note: These are the problems that are resolved with Load Balancer.

Key characteristics of Load Balancers

• Traffic Distribution: To keep any one server from becoming overburdened, load balancers divide incoming requests evenly among several servers.
• High Availability: Applications' reliability and availability are improved by load balancers, which divide traffic among several servers. The load balancer reroutes traffic to servers that are in good condition in the event that one fails.
• Scalability: By making it simple to add servers or resources to meet growing traffic demands, load balancers enable horizontal scaling.
• Optimization: Load balancers optimize resource utilization, ensuring efficient use of server capacity and preventing bottlenecks.
• Health Monitoring: Load balancers often monitor the health of servers, directing traffic away from servers experiencing issues or downtime.
• SSL Termination: Some load balancers can handle SSL/TLS encryption and decryption, offloading this resource-intensive task from servers.

How Load Balancer Works?

• Receives Incoming Requests: When users try to access a website or application, their requests first go to the load balancer instead of directly to a server.
• Checks Server Health: The load balancer continuously monitors the status of all servers. It checks which servers are healthy and ready to handle requests.
• Distributes Traffic: Based on factors like server load, response time or proximity, the load balancer forwards each request to the most appropriate server. This helps avoid any server getting overloaded.
• Handles Server Failures: If a server goes down or becomes unresponsive, the load balancer automatically stops sending traffic to that server and redirects it to others that are still functioning properly.
• Optimizes Performance: By spreading traffic efficiently and using healthy servers, load balancers improve overall performance and reduce delays.

Benefits of Load Balancer

• Better Performance - Distributes traffic across servers so no single server gets overloaded, reducing downtime and improving speed.
• Scalability - Works with auto-scaling to add more servers during high traffic and remove them when traffic is low.
• Failure Handling - Detects unhealthy servers and redirects traffic to healthy ones, keeping the system available.
• Prevents Bottlenecks - Handles sudden spikes in traffic smoothly by spreading requests evenly.
• Efficient Resource Use - Ensures all servers share the workload fairly.
• Session Persistence - Can maintain user sessions so apps that need continuous sessions (like shopping carts) work properly

Challenges of Load Balancer

• Single Point of Failure - If the load balancer itself goes down, it can disrupt traffic flow unless a backup exists.
• Cost and Complexity - Good load balancing solutions can be expensive and require proper setup and management.
• Configuration Issues - Setting up correctly can be tricky, especially for complex applications.
• Extra Overhead - Adds a small delay since every request passes through the load balancer.
• SSL Management - Handling encryption (SSL termination) at the balancer can make end-to-end security more complicated.