What is balancer?

A balancer, short for load balancer, is a device or software that sits between users and a group of servers. Its job is to receive incoming network requests and then spread (or “balance”) those requests across multiple servers so no single server gets overwhelmed.

Let's break it down

  • Incoming traffic: Every time someone clicks a link or sends a request, it first reaches the balancer.
  • Pool of servers: Behind the balancer are several identical servers (often called a “farm” or “cluster”) that can handle the work.
  • Distribution method: The balancer uses rules (like round‑robin, least connections, or health‑checks) to decide which server should get each request.
  • Health monitoring: It constantly checks if a server is up and healthy; if one fails, the balancer stops sending traffic to it.

Why does it matter?

  • Reliability: If one server crashes, the balancer redirects traffic to the others, keeping the service online.
  • Performance: By sharing the load, each server works less hard, which reduces response times for users.
  • Scalability: Adding more servers to the pool lets you handle more visitors without redesigning the whole system.

Where is it used?

  • Large websites and e‑commerce platforms (e.g., Amazon, Netflix)
  • Cloud services like AWS Elastic Load Balancing or Azure Load Balancer
  • Online gaming servers that need to serve many players simultaneously
  • API gateways that route requests to multiple microservices
  • Corporate intranets that balance internal application traffic

Good things about it

  • Provides high availability and fault tolerance.
  • Improves user experience with faster response times.
  • Makes it easy to add or remove servers as demand changes.
  • Can perform SSL termination, offloading encryption work from the servers.
  • Offers flexibility to route traffic based on geography, device type, or other criteria.

Not-so-good things

  • Adds an extra layer of hardware or software, increasing cost and complexity.
  • Misconfiguration can create bottlenecks or even a single point of failure.
  • Some balancing algorithms may introduce slight latency as requests are inspected.
  • Requires ongoing monitoring and maintenance to keep health checks accurate.
  • In very small setups, the overhead of a balancer might outweigh its benefits.