MultiCloud Classroom notes 21/Dec/2025

Reverse Proxy

• A reverse proxy is a server that stands in front of your application servers, recieves all client requests and forwards them to correct backend server
  
• Analogy

Guest  --> Reception Desk
                          --> Room Service
                          --> House Keeping
                          --> Restaurant

• Why Reverse proxy

Problems without Reverse Proxy	How Reverse Proxy Helps
Client should know every server ip	Hides backend servers
Hard to add/remove serves	Backend can change freely
No traffic control	smart rouging is possible
No central security	SSL, auth, filtering all at one place

Load Balancer

• A Load Balancer is a type of reverse proxy that distributes incoming requests across multiple backend servers
• Reverse Proxy vs Load Balancer

Reverse Proxy	Load Balancer
Forwards requests	Distributes Requests
Can route based on URL, headers	Chooses server based on Algorithm
Focus on abstraction	Focus on scalability and performance
May have single backend	Always have multiple backends

• Summary

Every Load balancer is a reverse proxy, but not each reverse proxy is a load balancer

• LB Algorithms
  • Round robin: Gives turns one by one
  • Least Connections: Gives work to the least busy server
  • IP Hash: Same USer -> same server
  • Weighted: Stron server gets more traffic.
    

Load Balancers according to OSI

• In real systems load balancers mostly work at Layer 7 and Layer

Layer 4 Loadbalancer

• What it understands
  • ip address
  • Port
  • TCP/UP
• What it does not see
  • URL’s
  • Headers
  • Cookies
• Characteristics
  • Very fast
  • Handles huge traffic
  • No smart Route
• Typical use cases
  • Database Servers
  • Game Servers
  • Non HTTP Traffic
  • High performace systems

Layer 7

• What it understands
  • URLs
  • HTTP Headers
  • Cookies
  • Host Names
  • HTTP MEthods
• It can forware the traffic based on context of request
• Example: if the request contains
  • /api/* forward theme to Api Servers
  • /admin/* forward them to admin servers
  • /login/* forward them to identity servers
  • /images/* forward to blob/image server
• Key characteristics
  • Smart routing
  • SSL Termination
  • Authentication possible
  • Slightly slower than layer 4
• Refer Here for de