Post on 27-Jun-2015
transcript
Social networking architectures what can we
learn
An enthusiasts view2
How do sites with a social networking angle figure globally?
3
As ranked by AlexaSite Global rankingFacebook 2YouTube 3Yahoo 4Windows Live 5Blogger 7Wikipedia 8Twitter 10
3 Principles4
3 common principles
1.Fast feature delivery is key
2.Cache everything everywhere
3.Relational data is dead
Interesting stats5
Facebook - Serve 120 million queries per second without a single join
37 Signals - Developed a production application serving over 4 million items using only 579 lines of code
Flickr - 2 Billion photos served without using relational databases
How did they do it?6
Nobody thought this was possible
Unencumbered by history or restrictive rules
Had to be creative in solving problems that nobody had experienced using very little capital outlay
3 Principles7
1.Fast feature delivery is key
2. Cache everything everywhere
3. Relational data is dead
Fast feature delivery is key8
Choose an appropriate language
Speed of development more important than speed of execution
Languages like PHP and Ruby commonly used for rapid development and deployment
Language is not religion9
3 Principles10
1. Fast feature delivery is key
2.Cache everything everywhere
3. Relational data is dead
Cache everything everywhere11
You need a really good reason not to cache data for reading
Local caching a good start but more than one server means duplicating the cache no group invalidation memory limited to how much spare RAM on the server
Most social networks use a distributed cache like memcached
Cache everything everywhere12
1. Check if the information is in the cache. If so, use it
2. If not, query the database put the result in the cache
3. On update delete from the cache. The next user goes to the database
function get_foo(int userid) { result = memcached_fetch("userrow:" + userid);
if (!result) { result = db_select("SELECT * FROM users WHERE userid = ?", userid); memcached_add("userrow:" + userid, result);
} return result;
Responsivness is key13
3 Principles14
1. Fast feature delivery is key
2. Cache everything everywhere
3.Relational data is dead
Everybody wants to use a database15
Relational issue No 1 - Normalisation16
Relational databases do not scale well because of normalisation
Why normalise?- reduce storage space- reduce anomalies
Today - storage is cheap- as data gets larger, joins are
expensive
Relational issue No 2 - Transactions17
ACID principles govern transactions
Relational databases do not scale well because of transactions
After relational18
Use BASE (basically available, soft state, eventually consistent)
Shard Data
Favour Name value pair stores over relational databases
Lessons for enterprise19
Design of software should always be it depends.
Test your most basic assumptions
1. Dynamic languages and frameworks may be suitable to deliver a feature quickly
2. You don't need an RDBMS for everything, especially if you need huge scale
3. You should always cache data for read (unless you shouldn’t)
Fresh ideas always welcome20
Or find me here22