Cassandra is a good fit for write heavy workload, as it is optimized for write...

Agreed. You can achieve very high productivity if you use Scala and Java properly.

I just notice VIA and HTC are founded by the same woman[1], and I know the financial situation of VIA is not good...

[1] http://blog.laptopmag.com/2011-most-important-women-in-mobil...

"A user's data is stored in a single row in HBase"

Some column families of HBase can be accumulated to hundreds of mega bytes very easily, I'm afraid...

The token in cookie stored by browser is portable, either. How can web apps prevent the attackers exploiting the system from stealing the cookie token?

When different customers use different key to encrypt the data, even if the source is the same, the outcome is different. So it is not feasible to do de-duplication across different customers' data, unless all of them use the same key.

Does SpiderOak only provide backup service? Erasure encoding is efficient for cold data. Do you use erasure encoding to distribute the hot data across clusters?

I use patch queue[1] to manage these short lived branch, and it works for my purpose. You just pop the patches and delete them all when you want to prunge the branch. It also make it easy for others to review your code.

If these short-lived branch will be merged back shortly. Bookmark is another alternatives.

[1] http://mercurial.selenic.com/wiki/MqExtension [2] http://mercurial.selenic.com/wiki/BookmarksExtension

I'm aware of both. Personally I find this to be an inferior solution. Using a patch queue as a local branch just feels wrong. Neither is using bookmarks an effective solution. Both solution make the decision to branch a much more deliberate process, and in the end you still don't get a branch that is equal to its peers.

As the result, in hg, you have to decide in advance "what kind of branch" it will be -- or you have to get in the habit of using mq's for everything -- and this just not a natural experience especially for a DVCS where branching is just fundamental.

If I tries to shorten the url of http://google.com several times, goo.gl always give back different result. I just wonder will goo.gl merge theses url together sometime later?

This interesting found implies how goo.gl is designed. They prefer writing directly to avoid duplication check and random seek caused by the check. And they though most of the urls are cold so it is not essential to merge them together to keep the hot cache small.

Or they assume nobody wants to play the system in this way. :-)

They have to do different URLs each time because you get stats for each shortened URL.

The architecture of MegaStore is so complicated... There are so many roles in the system, e.g. stateless replicate server, different stateful paxos instances, stateful co-coordinator, bigtable and other auxilary roles.

I suspect some roles are added later because the original implementation does not meet their design goal, as patch to normal software product.

It is a nightmare for operation engineers of GAE.