Published on

Load Balancing Algorithms - A Simple Guide

When a website or app gets lots of users, it needs more than one server to handle all the traffic. But how do we make sure each server gets a fair share of the work? That's where load balancing algorithms come in.

A load balancing algorithm helps distribute incoming requests across multiple servers. The goal is to make the system fast, reliable, and efficient. Let's explore the most common types in simple terms.

1. 🌀 Round Robin

How it works: Requests are sent to each server one after another, like taking turns in a circle.

✅ Pros:

  • Easy to set up
  • Good for servers with equal power

❌ Cons:

  • Doesn't check how busy a server is
  • Not ideal for keeping user sessions on the same server

📌 Best for: Simple apps and equal-capacity servers.

2. 📉 Least Connections

How it works: Sends new requests to the server with the fewest active connections.

✅ Pros:

  • Balances work better than Round Robin
  • Adjusts to traffic changes

❌ Cons:

  • More complex
  • Needs to track open connections

📌 Best for: Apps with different traffic levels or session-heavy services.

3. ⚖️ Weighted Round Robin

How it works: Similar to Round Robin, but gives more requests to stronger servers.

✅ Pros:

  • Efficient use of powerful servers
  • Easy to adjust weights if server power changes

❌ Cons:

  • Doesn't check real-time load
  • Needs correct weight setup

📌 Best for: Servers with different capabilities.

4. 🧮 Weighted Least Connections

How it works: Like Least Connections, but also considers server strength (weights).

✅ Pros:

  • Smart and adaptive
  • Uses powerful servers more efficiently

❌ Cons:

  • Complex to manage
  • Needs both connection tracking and weight setup

📌 Best for: Busy apps and mixed server environments.

5. 🌍 IP Hash

How it works: Uses a hash of the user's IP address to always send them to the same server.

✅ Pros:

  • Keeps users connected to the same server (good for logins or shopping carts)
  • Easy to set up

❌ Cons:

  • Load may be uneven
  • Changing server count breaks consistency

📌 Best for: Apps needing session persistence.

6. ⚡ Least Response Time

How it works: Sends requests to the server that responds the fastest.

✅ Pros:

  • Low latency
  • Smart real-time routing

❌ Cons:

  • Needs constant monitoring
  • Can be affected by temporary slowdowns

📌 Best for: Apps needing fast replies, like games or video streaming.

7. 🎲 Random

How it works: Picks a server at random for each new request.

✅ Pros:

  • Very easy to use
  • No tracking needed

❌ Cons:

  • May overload some servers
  • Not ideal for session-based apps

📌 Best for: Simple apps with equal servers.

8. 📶 Least Bandwidth (Optional Bonus)

How it works: Sends traffic to the server using the least amount of bandwidth at the moment.

✅ Pros:

  • Efficient for media-heavy content

❌ Cons:

  • Needs bandwidth tracking

📌 Best for: Media streaming or large downloads.

🏁 Conclusion

Choosing the right load balancing algorithm depends on:

  • Your app's needs (speed, session handling, simplicity)
  • Your server setup (equal or different strengths)
  • Traffic patterns (steady or changing)

A smart load balancer with the right algorithm makes your application faster, more stable, and ready to scale.