If you design it right you can benefit from strong consistency in the situations you need it while still not hitting the 1 write/sec/group cap, see the Google IO talk about it (in particular the user centric design): http://www.youtube.com/watch?v=xO015C3R6dw
And the slides of the talk: http://static.googleusercontent.com/external_content/untrusted_dlcp/www.google.com/en/us/events/io/2011/static/presofiles/more_9s_under_the_covers_of_the_high_replication_datastore.pdf As described in that talk, you want strong consistency in particular for a user's own posts (i.e. it's annoying as a user if you post and don't see your own post right away..) Cheers, Gabriel On Oct 22, 3:16 pm, Mos <mosa...@googlemail.com> wrote: > I'm still in a design phase of a new App Engine application and I'm > wondering > if it makes sense to go *without* using any Entity Groups. > > My application's data-model is similar to a discussion-forum. > It has Postings, Comments, Users, Ratings and so on. If the application > becomes successful, there will be significant write operations on > Postings, Comments and Ratings. > > If I would model hierarchical *Entity-Groups* (e.g. starting from a > User-Root), I would > have the following *advantages*: > +1: Transactional behavior during writes > +2: Queries are strongly consistent > +3: For hierachical data-structures, fast ancestor queries are available > > But *Entity-Groups* introduce also some *disadvantages*: > -1: Limitation in write throughput (in worst case just 1 write per > second on an entity group) > -2: Inflexible and a more complex data-model, which makes it harder to add > or re-factor relationships (forces "owned-relations" all over your > application) > > *I think all together the disadvantages outweigh the advantages for a > typical web application like mine.* > The limitation for writes seems to be a significant disadvantage. Ok, you > can work around this with sharding but this makes > you data-model even more complex. > And an hierarchical data-model which is technically motivated and not > related to your domain seems to be a bad idea. > > On the other hand transactions during write operations are often not > necessary ("the last one wins"). > Hierarchical searches are not needed most of the time. > > The only issue I'm not sure about is the advantage of "Queries are strongly > consistent "? > What does it mean if they are not strongly consistent? > Is this just an issue for a small time frame when new data are written? Once > the data is > stored and replicated this shouldn't be an issue at all, or? > > I'm happy about feedback! > > Thanks > Mos -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to google-appengine@googlegroups.com. To unsubscribe from this group, send email to google-appengine+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en.
