system design

following these 4 steps can help you tackle any system design problem.

example: design a calendar

1. scale

   • queries per second. Read? Write? Use harddisk or RAM?
   • does latency matter?
   • what features? (user register, can create event, book a conference room, etc)
   • what user interface? what platform?

2. service

   • user service (MySql) User userId userName email password registeredAt

   • calendar service (NoSql) Event eventId eventName startTime endTime users notes status

   • image, files storage: file system

   • user interface (client-side program) browser? mobile app?

3. storage

   • user service: mysql
   • calendar service:
   • image, files storage

4. functionality in detai

   • what api?
   • query(user, day)
     • insert(user, event)
     • delete(user, event)
   • what's the structure of HTTP response?

storage pros vs. cons

MySql

1. schema must be maintained and kept in sync between application and database

   Good:

2. great for solutions where every record has the same structure
3. good for structured data
4. relationships are often captured in normalized models using joins to resolve references across tables

5. strong consistency

   Bad:

6. adding new property on table schema requires backfill

NoSql

1. dynamic / flexible schema

2. relationships are often captured by denormalizing data and presenting all data for an object in a single record

   Good

3. new properties can be added on the fly

Redis: NoSql database used for caching