Jay Marcyes

Good general "how we scaled" article

The whole article gets into a lot of details about how they scaled Flickr and well worth the read if you are into scaling web apps. Specifically I really like the db notes:

Database is the hardest part to scale. If we can, best to avoid the issue altogether and just buy bigger hardware. Dual-quad opteron with 16GB RAM can get you a long way.

What do you do when the hardware can’t keep up? We do a lot more reading than writing. Somewhere between 80/20 or 90/10 ratio of read/write. “Only a few people who like to caption pictures of kittens on the internet - but a whole lot of people who like to look at them.”

Replication is the solution for the read write problem. Master-slave replication. Add more slaves, 1 master 3 slaves = 4 times the read power. Flickr is 6 reads for every write.  Problem is what happens when we need to push more writes? As we need more writes this doesn’t scale well - have to add a lot more boxes.

MySQL query cache has bad performance in most cases. MySQL query cache: for any read query stores a pointer to the result if you perform the exact same query. Any write flushes it, though. So if you do 10 reads for every 1 write you’re unlikely to get a hit before cache is invalidated. If you only write once an hour or day then this is a really good thing. Otherwise turn it off.

One of the best writeups on what DB sharding is and how you can implement it that I have read.

Jeff giving props to the PlentyOfFish guy and his scaling awesomeness. The money quote on both blogs:

The problem with free is that every time you double the size of your
database the cost of maintaining the site grows 6 fold. I really
underestimated how much resources it would take, I have one database table now that exceeds 3 billion records. The bigger you get as a free site the less money you make per visit and the more it costs to
service a visit. via

Still, he has managed to build PlentyOfFish on just a handful of servers, maybe I should look into .Net.

Also Check out this look at PlentyOfFish's architecture.

Update June 24, 2009: Jeff just wrote a piece on "scaling up" vs. "scaling out" that also uses Plenty of Fish as the example.