Learning Objectives

By the end of this chapter, you should be able to:

• Explain what a load balancer is and why it is used.
• Understand how load balancers distribute traffic across multiple servers.
• Differentiate between Layer 4 and Layer 7 load balancing.
• Compare common load balancing algorithms.
• Understand health checks and why they are essential.
• Explain sticky sessions and when they should or should not be used.
• Understand high availability and fault tolerance.
• Differentiate between active-active and active-passive deployments.
• Understand AWS Elastic Load Balancing (ALB, NLB, and GWLB).
• Troubleshoot common production issues involving load balancers.

Introduction

Imagine a popular restaurant with only one cashier.

When only a few customers arrive, everything runs smoothly.

However, during lunch hours, hundreds of customers begin lining up.

Soon:

• Customers wait too long.
• The cashier becomes overwhelmed.
• Orders are delayed.