What is load balancing
Load balancing is the process of distributing incoming network traffic across multiple targets, such as EC2 instances, containers, or IP addresses, to improve application availability, fault tolerance, and scalability [citation:1].
Load balancing is the process of efficiently distributing incoming network traffic across a group of backend servers, also known as a target group. Its primary goals are to prevent any single server from becoming overwhelmed, to ensure high availability by rerouting traffic if a server fails, and to enable seamless scaling as application demand grows.
Scenario Questions
- 1
We have a simple web app running on two EC2 instances behind a Classic Load Balancer. How would you configure the health check so that traffic stops being sent to a failing instance?
- 2
If you add a new EC2 instance to an existing Application Load Balancer target group, what steps are required for it to start receiving traffic?
- 3
What happens to existing connections when you change the listener port on an ALB?
- 1
Your service started returning 502 errors after you switched from a Classic Load Balancer to an Application Load Balancer. Walk me through how you would debug the issue.
- 2
When scaling out an Auto Scaling group behind an ALB, how do you decide between using round‑robin vs. least‑connections routing, and what trade‑offs does each bring?
- 3
Explain why you might configure sticky sessions on a load balancer, and what impact that has on scaling.
- 1
Design a high‑availability architecture for a globally distributed web service using AWS load balancers, considering latency, failover, and cost.
- 2
Your load balancer is experiencing high latency spikes during traffic bursts. What metrics would you examine, and how would you mitigate the problem?
- 3
How would you migrate a legacy monolithic app using a single ELB to a microservices architecture with multiple target groups without downtime?
- 1
At a large enterprise, multiple teams own different services behind a shared Network Load Balancer. How would you structure routing rules, health checks, and governance to minimize cross‑team impact?
- 2
Discuss the long‑term operational considerations of moving from regional load balancers to a global accelerator solution. What are the trade‑offs in terms of performance, cost, and complexity?
- 3
If you need to support both HTTP/2 and TCP traffic for different clients, how would you architect the load balancing layer in AWS while keeping a single entry point?
Follow-up Questions
- ❓Can you give an example where you’d prefer a Network Load Balancer over an Application Load Balancer?
- ❓How does the choice of health‑check protocol affect instance availability?
- ❓What are the cost implications of using multiple load balancers versus a single one with path‑based routing?