Categorize system design problems based on difficulty level

README.md

@@ -31,49 +31,51 @@ This repository contains System Design articles and videos which are useful duri
 
 
 ## System Design Interview Problems
-
+### Easy
 - [Design URL Shortener like TinyURL](https://www.youtube.com/watch?v=fMZMm_0ZhK4)
 - [Design Text Storage Service like Pastebin](https://www.youtube.com/watch?v=josjRSBqEBI)
-- [Design Netflix](https://www.youtube.com/watch?v=psQzyFfsUGU)
-- [Design Youtube](https://www.youtube.com/watch?v=jPKTo1iGQiE)
+- [Design Content Delivery Network (CDN)](https://www.youtube.com/watch?v=8zX0rue2Hic)
+- [Design Parking Garage](https://www.youtube.com/watch?v=NtMvNh0WFVM)
+- [Design Vending Machine](https://www.youtube.com/watch?v=D0kDMUgo27c)
+- [Design Distributed Key-Value Store](https://www.youtube.com/watch?v=rnZmdmlR-2M)
+- [Design Distributed Cache](https://www.youtube.com/watch?v=iuqZvajTOyA)
+- [Design Distributed Job Scheduler](https://towardsdatascience.com/ace-the-system-design-interview-job-scheduling-system-b25693817950)
+- [Design Authentication System](https://www.youtube.com/watch?v=uj_4vxm9u90)
+- [Design Unified Payments Interface (UPI)](https://www.youtube.com/watch?v=QpLy0_c_RXk)
+### Medium
 - [Design Instagram](https://www.youtube.com/watch?v=VJpfO6KdyWE)
-- [Design Twitter](https://www.youtube.com/watch?v=wYk0xPP_P_8)
-- [Design E-commerce Store like Amazon](https://www.youtube.com/watch?v=EpASu_1dUdE)
+- [Design Tinder](https://www.youtube.com/watch?v=tndzLznxq40)
 - [Design WhatsApp](https://www.youtube.com/watch?v=vvhC64hQZMk)
 - [Design Facebook](https://www.youtube.com/watch?v=9-hjBGxuiEs)
-- [Design File Sharing System like Dropbox](https://www.youtube.com/watch?v=U0xTu6E2CT8)
-- [Design Autocomplete for Search Engines](https://www.youtube.com/watch?v=us0qySiUsGU)
+- [Design Twitter](https://www.youtube.com/watch?v=wYk0xPP_P_8)
+- [Design Reddit](https://www.youtube.com/watch?v=KYExYE_9nIY)
+- [Design Netflix](https://www.youtube.com/watch?v=psQzyFfsUGU)
+- [Design Youtube](https://www.youtube.com/watch?v=jPKTo1iGQiE)
 - [Design Google Search](https://www.youtube.com/watch?v=CeGtqouT8eA)
+- [Design E-commerce Store like Amazon](https://www.youtube.com/watch?v=EpASu_1dUdE)
+- [Design Spotify](https://www.youtube.com/watch?v=_K-eupuDVEc)
+- [Design TikTok](https://www.youtube.com/watch?v=Z-0g_aJL5Fw)
+- [Design Shopify](https://www.youtube.com/watch?v=lEL4F_0J3l8)
 - [Design Airbnb](https://www.youtube.com/watch?v=YyOXt2MEkv4)
-- [Design Tinder](https://www.youtube.com/watch?v=tndzLznxq40)
+- [Design Autocomplete for Search Engines](https://www.youtube.com/watch?v=us0qySiUsGU)
+- [Design Rate Limiter](https://www.youtube.com/watch?v=mhUQe4BKZXs)
+- [Design Distributed Message Queue like Kafka](https://www.youtube.com/watch?v=iJLL-KPqBpM)
+- [Design Flight Booking System](https://www.youtube.com/watch?v=qsGcfVGvFSs)
+- [Design Online Code Editor](https://www.youtube.com/watch?v=07jkn4jUtso)
 - [Design Stock Exchange System](https://www.youtube.com/watch?v=dUMWMZmMsVE)
-- [Design Google Maps](https://www.youtube.com/watch?v=jk3yvVfNvds)
-- [Design Distributed Web Crawler](https://www.youtube.com/watch?v=BKZxZwUgL3Y)
+- [Design an Analytics Platform (Metrics & Logging)](https://www.youtube.com/watch?v=kIcq1_pBQSY)
+- [Design Notification Service](https://www.youtube.com/watch?v=CUwt9_l0DOg)
+- [Design Payment System](https://www.youtube.com/watch?v=olfaBgJrUBI)
+### Hard
 - [Design Location Based Service like Yelp](https://www.youtube.com/watch?v=M4lR_Va97cQ)
 - [Design Uber](https://www.youtube.com/watch?v=umWABit-wbk)
-- [Design Ticket Booking System like BookMyShow](https://www.youtube.com/watch?v=lBAwJgoO3Ek)
-- [Design Spotify](https://www.youtube.com/watch?v=_K-eupuDVEc)
 - [Design Food Delivery App like Doordash](https://www.youtube.com/watch?v=iRhSAR3ldTw)
-- [Design Zoom](https://www.youtube.com/watch?v=G32ThJakeHk)
-- [Design Shopify](https://www.youtube.com/watch?v=lEL4F_0J3l8)
 - [Design Google Docs](https://www.youtube.com/watch?v=2auwirNBvGg)
-- [Design TikTok](https://www.youtube.com/watch?v=Z-0g_aJL5Fw)
-- [Design Reddit](https://www.youtube.com/watch?v=KYExYE_9nIY)
+- [Design Google Maps](https://www.youtube.com/watch?v=jk3yvVfNvds)
+- [Design Zoom](https://www.youtube.com/watch?v=G32ThJakeHk)
+- [Design File Sharing System like Dropbox](https://www.youtube.com/watch?v=U0xTu6E2CT8)
+- [Design Ticket Booking System like BookMyShow](https://www.youtube.com/watch?v=lBAwJgoO3Ek)
+- [Design Distributed Web Crawler](https://www.youtube.com/watch?v=BKZxZwUgL3Y)
 - [Design Code Deployment System](https://www.youtube.com/watch?v=q0KGYwNbf-0)
-- [Design Distributed Message Queue like Kafka](https://www.youtube.com/watch?v=iJLL-KPqBpM)
 - [Design Distributed Cloud Storage like S3](https://www.youtube.com/watch?v=UmWtcgC96X8)
-- [Design Distributed Job Scheduler](https://towardsdatascience.com/ace-the-system-design-interview-job-scheduling-system-b25693817950)
-- [Design Rate Limiter](https://www.youtube.com/watch?v=mhUQe4BKZXs)
 - [Design Distributed Locking Service](https://www.youtube.com/watch?v=v7x75aN9liM)
-- [Design Distributed key-value store](https://www.youtube.com/watch?v=rnZmdmlR-2M)
-- [Design Distributed Cache](https://www.youtube.com/watch?v=iuqZvajTOyA)
-- [Design Notification Service](https://www.youtube.com/watch?v=CUwt9_l0DOg)
-- [Design Metrics & Logging Service](https://www.youtube.com/watch?v=kIcq1_pBQSY)
-- [Design Content Delivery Network (CDN)](https://www.youtube.com/watch?v=8zX0rue2Hic)
-- [Design Parking Garage](https://www.youtube.com/watch?v=NtMvNh0WFVM)
-- [Design Flight Booking System](https://www.youtube.com/watch?v=qsGcfVGvFSs)
-- [Design Online Code Editor](https://www.youtube.com/watch?v=07jkn4jUtso)
-- [Design Vending Machine](https://www.youtube.com/watch?v=D0kDMUgo27c)
-- [Design Authentication System](https://www.youtube.com/watch?v=uj_4vxm9u90)
-- [Design Payment System](https://www.youtube.com/watch?v=olfaBgJrUBI)
-- [Design UPI](https://www.youtube.com/watch?v=QpLy0_c_RXk)