

Google Megastore - 3 Billion Writes and 20 Billion Read Transactions Daily - timf
http://highscalability.com/blog/2011/1/11/google-megastore-3-billion-writes-and-20-billion-read-transa.html

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rbranson
_Writes are limited to 1 per second, so HRD is not a good match when high
usage is expected._

This is per entity group, and it's not a strict limitation, it's an
expectation of performance.

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redstripe
_"Backups and redundancy are achieved via synchronous replication, snapshots,
and incremental log backups."_

That's nice but you can't access these backups. They are there for the system
failing - not for your own needs. RAID is not a backup strategy.

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equark
It's built on top of bigtable, so presumably users can request the state of an
object at any point in time just by specifying a timestamp with their query.

~~~
redstripe
I don't think that's an ability that's exposed to app engine users. I don't
see any mention of it:
<http://code.google.com/appengine/docs/python/datastore/>

