On Sun, Jan 8, 2012 at 8:12 AM, jon <[email protected]> wrote: > > It's so expensive that the Relation Index Entity technique > proposed by your own Brett Slatkin has become cost prohibitive. > > If Twitter was built on GAE using Relation Index Entity, each tweet made > by a popular user with 1 million followers would cost $1 each.
I make it $2, as there is both an ascending and descending index on the MessageIndex.receivers list property, even though you only need one for equality matching. Actually, it's probably more like $3 as you need to get tweets in date order, which will require a compound index on receivers and date. This is looking pretty inefficient as $2 of the $3 cost is the overhead of two unused single property indexes. > Let's say there are 1000 such users on Twitter. And if each one tweeted 10 > times a day, the cost would be $10,000 a day! Apparently people tweet 250,000,000 times a day (2,900/sec), and the average user has 136 followers. If twitter used the relatiion index pattern on App Engine they might spend aprox. $105,000/day for write opperations to store tweets, about $38 million per year (or $1.20/sec). -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en.
