📘 Load Balancer – Complete Concept


              📘 Load Balancer – Complete Concept 

🔹 1. What is a Load Balancer?

A Load Balancer distributes incoming network traffic across multiple servers to ensure:

  • High availability
  • Better performance
  • No single server overload

👉 Example: Instead of 1 server handling 10,000 users, LB splits traffic across 5 servers.


🔹 2. Why Do We Need It?

Without LB:

  • Server crash = whole app down 
  • Slow response under heavy traffic 

With LB:

  • Fault tolerance 
  • Scalability 
  • High performance 

🧠 First: What is IP & Port?

  • IP address = identifies a machine
    👉 like house address (192.168.1.1)
  • Port = identifies a service inside that machine
    👉 like room number
    • 80 → HTTP
    • 443 → HTTPS
    • 3306 → MySQL

🔹 3. Types of Load Balancer

(A) Based on Layer (OSI Model)

1. Layer 4 (Transport Level)

  • Works on IP + Port
  • Faster, less intelligent
  • Example: TCP routing

2. Layer 7 (Application Level)

  • Works on HTTP/HTTPS
  • Can route based on:
    • URL (/login, /payment)
    • Headers
  • More flexible

(B) Deployment Type

  • Hardware LB → Expensive (F5, etc.)
  • Software LB → Common
    • NGINX
    • HAProxy
  • Cloud LB
    • AWS Elastic Load Balancing

🔹 4. Load Balancing Algorithms

1. Round Robin

  • Requests distributed one by one
    👉 Server1 → Server2 → Server3

2. Least Connections

  • Send request to server with fewer active users

3. IP Hash

  • Same user always goes to same server

4. Weighted Round Robin

  • Powerful servers get more requests

🔹 5. Important Concepts

 Health Check

  • LB continuously checks servers
  • If server is down → stops sending traffic

 Auto Scaling

  • Add/remove servers automatically based on traffic

 SSL Termination

  • LB handles HTTPS encryption
  • Reduces load on backend servers 

 Session Persistence (Sticky Sessions)

  • Same user → same server
  • Useful for login sessions

Comments

Post a Comment

Popular posts from this blog

Two Sum II - Input Array Is Sorted

 Given a 1-indexed array of integers numbers that is already sorted in non-decreasing order , find two numbers such that they add up to a specific target number. Let these two numbers be numbers[index1] and numbers[index2] where 1 <= index1 < index2 <= numbers.length. Return the indices of the two numbers, index1 and index2, added by one as an integer array [index1, index2] of length 2. The tests are generated such that there is exactly one solution. You may not use the same element twice. Your solution must use only constant extra space .   Example 1: Input: numbers = [2,7,11,15], target = 9 Output: [1,2] Explanation: The sum of 2 and 7 is 9. Therefore, index1 = 1, index2 = 2. We return [1, 2]. Example 2: Input: numbers = [2,3,4], target = 6 Output: [1,3] Explanation: The sum of 2 and 4 is 6. Therefore index1 = 1, index2 = 3. We return [1, 3]. Example 3: Input: numbers = [-1,0], target = -1 Output: [1,2] Explanation: The sum of -1 and 0 is -1. Therefore index1 = 1,...
Read more

Comparable Vs. Comparator in Java

  In Java , Comparable and Comparator both are interfaces used to sort objects. Comparable It defines  natural ordering  within a class. It is implemented  inside  the class being sorted. It uses the compareTo() method. It allows sorting  by one one . Comparable provides a  single sorting sequence . In other words, we can sort the collection on the basis of a single element such as id, name, and price. Comparable  affects the original class , i.e., the actual class is modified. Comparable is present in  java.lang  package. We can sort the list elements of Comparable type by  Collections.sort(List)  method. Only one compareTo() method can be implemented, restricting flexibility. Comparator It defines  custom sorting logic It is implemented  in a separate class  or using lambda expressions . It uses the compare() method. It allows sorting  by multiple criteria . The Comparator provides  multiple sorting...
Read more

Increasing Triplet Subsequence

 Given an integer array nums, return true if there exists a triple of indices (i, j, k) such that i < j < k and nums[i] < nums[j] < nums[k]. If no such indices exists, return false.   Example 1: Input: nums = [1,2,3,4,5] Output: true Explanation: Any triplet where i < j < k is valid. Example 2: Input: nums = [5,4,3,2,1] Output: false Explanation: No triplet exists. Example 3: Input: nums = [2,1,5,0,4,6] Output: true Explanation: The triplet (3, 4, 5) is valid because nums[3] == 0 < nums[4] == 4 < nums[5] == 6. Brute Force : Failed for some testcase class Solution {     public boolean increasingTriplet ( int [] nums ) {         int n = nums . length ;         int i = 0 ;         int j =i+ 1 ;         int k =j+ 1 ;         while (i <n && j<n && k<n)         {         if (nums...
Read more