scalability for dummies

• That leads to the first golden rule for scalability: every server contains exactly the same codebase and does not store any user-related data, like sessions or profile pictures, on local disc or memory.

• Sessions need to be stored in a centralized data store which is accessible to all your application servers. It can be an external database or an external persistent cache, like Redis.

• Database will become a bottleneck when app get slower and slower. Path #1, stick to Mysql, do master-slave replication, sharding, denormalization, sql tuning. Path #2, use NoSQL.

• When database is still a bottleneck, you can consider caching!

• The author prefer caching an object of data. Something like wrapping the data into a class.

  • user sessions (never use the database!)
  • fully rendered blog articles
  • activity streams
  • user<->friend relationships

• Async stuff

Reference

• http://www.lecloud.net/tagged/scalability