Why Network Load Balancer (NLB) in AWS? - Purpose & Use Cases

The Big Idea

What if your website could handle a sudden flood of visitors without breaking or slowing down?

The Scenario

Imagine you run a popular online store. When many customers visit at once, your single server gets overwhelmed. You try to manually direct each customer to different servers by changing IP addresses or DNS settings yourself.

The Problem

This manual way is slow and confusing. It causes delays, mistakes, and sometimes customers get lost or see errors. You can't handle sudden traffic spikes or keep your site running smoothly.

The Solution

A Network Load Balancer (NLB) automatically spreads incoming traffic across many servers. It quickly directs each request to a healthy server without you lifting a finger, even during huge traffic bursts.

Before vs After

✗ Before

Change DNS records manually to point to different servers.

✓ After

Use NLB to automatically distribute traffic to multiple servers.

What It Enables

It enables your application to handle millions of users smoothly by balancing traffic efficiently and reliably.

Real Life Example

When a big sale starts, an NLB ensures thousands of shoppers connect to different servers without crashing your website.

Key Takeaways

Manual traffic management is slow and error-prone.

NLB automates traffic distribution for high availability.

It supports massive scale and improves user experience.

Practice

1. What is the primary purpose of an AWS Network Load Balancer (NLB)?

easy

A. To efficiently distribute TCP/UDP traffic at the connection level

B. To manage HTTP requests with advanced routing rules

C. To store and retrieve data in a scalable way

D. To provide a user interface for managing AWS resources

Solution

1. Step 1: Understand NLB's traffic handling

   NLB works at the connection level and handles TCP/UDP traffic efficiently.

2. Step 2: Compare with other AWS services

   Unlike Application Load Balancer, NLB does not manage HTTP features but focuses on low latency and high throughput for TCP/UDP.

3. Final Answer:

   To efficiently distribute TCP/UDP traffic at the connection level -> Option A

4. Quick Check:

   NLB purpose = TCP/UDP load balancing [OK]

Hint: NLB handles TCP/UDP, not HTTP features [OK]

Common Mistakes:

• Confusing NLB with Application Load Balancer
• Thinking NLB manages HTTP routing
• Assuming NLB stores data

2. Which of the following is a valid characteristic of an AWS Network Load Balancer (NLB)?

easy

A. Only supports HTTP and HTTPS protocols

B. Requires manual scaling for high traffic

C. Automatically modifies HTTP headers

D. Supports static IP addresses for the load balancer

Solution

1. Step 1: Identify NLB features

   NLB supports static IP addresses, which is useful for fixed IP requirements.

2. Step 2: Eliminate incorrect options

   NLB does not only support HTTP/HTTPS (it supports TCP/UDP), does not modify HTTP headers, and scales automatically.

3. Final Answer:

   Supports static IP addresses for the load balancer -> Option D

4. Quick Check:

   Static IP support = true for NLB [OK]

Hint: NLB supports static IPs, unlike ALB [OK]

Common Mistakes:

• Thinking NLB only supports HTTP/HTTPS
• Assuming NLB modifies HTTP headers
• Believing NLB requires manual scaling

3. Given an NLB configured to balance TCP traffic across three targets, what happens if one target becomes unhealthy?

medium

A. NLB stops sending traffic to the unhealthy target and continues with healthy ones

B. NLB sends traffic evenly to all targets regardless of health

C. NLB shuts down until the unhealthy target recovers

D. NLB redirects traffic to a backup Application Load Balancer

Solution

1. Step 1: Understand NLB health checks

   NLB performs health checks and routes traffic only to healthy targets.

2. Step 2: Analyze behavior on unhealthy target

   If a target is unhealthy, NLB excludes it from routing until it recovers.

3. Final Answer:

   NLB stops sending traffic to the unhealthy target and continues with healthy ones -> Option A

4. Quick Check:

   Health checks exclude unhealthy targets [OK]

Hint: NLB routes only to healthy targets [OK]

Common Mistakes:

• Assuming NLB sends traffic to unhealthy targets
• Thinking NLB stops completely on failure
• Believing NLB redirects to ALB automatically

4. You configured an NLB but notice it is not distributing UDP traffic as expected. What is the most likely cause?

medium

A. Health checks are disabled for the target group

B. The target group is configured for TCP instead of UDP

C. NLB does not support UDP traffic

D. NLB requires HTTP listeners for UDP traffic

Solution

1. Step 1: Check protocol configuration

   NLB supports UDP, but the target group must be set to UDP to handle UDP traffic.

2. Step 2: Identify misconfiguration

   If the target group is set to TCP, UDP traffic won't be routed correctly.

3. Final Answer:

   The target group is configured for TCP instead of UDP -> Option B

4. Quick Check:

   Target group protocol must match traffic [OK]

Hint: Match target group protocol to traffic type [OK]

Common Mistakes:

• Thinking NLB does not support UDP
• Ignoring target group protocol settings
• Assuming health checks cause traffic issues

5. You need to design a highly scalable system that requires static IP addresses and low latency for millions of TCP connections. Which AWS load balancer should you choose and why?

hard

A. Gateway Load Balancer, because it manages HTTP and TCP traffic with static IPs

B. Application Load Balancer, because it supports HTTP routing and static IPs

C. Network Load Balancer, because it supports static IPs and handles millions of TCP connections with low latency

D. Classic Load Balancer, because it is the newest and fastest option

Solution

1. Step 1: Identify requirements

   The system needs static IPs, low latency, and support for millions of TCP connections.

2. Step 2: Match requirements to load balancer features

   NLB supports static IPs, is designed for extreme scalability, and handles TCP traffic efficiently with low latency.

3. Step 3: Eliminate incorrect options

   ALB focuses on HTTP, Classic LB is older and less scalable, Gateway LB is for network appliances, not general TCP load balancing.

4. Final Answer:

   Network Load Balancer, because it supports static IPs and handles millions of TCP connections with low latency -> Option C

5. Quick Check:

   Static IP + TCP + scalability = NLB [OK]

Hint: For static IP and TCP scale, choose NLB [OK]

Common Mistakes:

• Choosing ALB for TCP static IP needs
• Confusing Classic LB as newest
• Assuming Gateway LB handles general TCP load balancing