1. Sharding and More
weng.wei@zalora.sg

2. • Sharding is about scaling
• scaling up VS scaling out

3. Scaling Out
• Add more nodes
• Each node shared nothing

4. Key / Value
• server = serverlist[ hash(key) %
len(serverlist) ]

5. Relational DB
• On Primary Key
• On Index

6. Middle layer
• MySQL Proxy

7. Client Side
• Memcached client
• ORM

8. Limitation
• No joining
• Join on the same shard is OK
• Data maintenance

9. Pre-Sharding
• Move database is easier than move data

10. Problem of sharding
• serverlist[ hash(key) % len(serverlist)

11. Consistent Hash
• ketama from last.fm
• De facto Standard for memcached

12. Do we use sharding?
• Memcached Client
• MySQL for different ventures

13. SQL vs NoSQL
• NoSQL is “Not Only SQL”
• NoSQL completes SQL, but not replaces it

14. NoSQL is about
• Performance?
• Scaling (easier to shard)?
• Flexibility (schema-less)?

15. Performance
• Memcacahed is faster than MySQL?
• SQL faster than K/V?
• Memory faster than disk?

16. MySQL for K/V
• handler socket

17. Schema - less
• Friendfeed’s solution
• Table as secondary index, then shard

18. • No silver bullet
• Trade off