3 ms·

I think your math is off here. Basically you end up with this equation cost = ((NumOfUsers * avgMsgsRevceivedPerUser)/maxWritesPerCPU) * costOfCPU There is n

by hank777 18y ago

I think your math is off here. Basically you end up with this equation cost = ((NumOfUsers * avgMsgsRevceivedPerUser)/maxWritesPerCPU) * costOfCPU There is nothing quadratic here. Your are able to scale linearly with the number of messages received in the system. There is a fixed cost per message received which is exactly what you want. By the way, this is exactly how the internet mail system works and it is why it is so scalable.

nostrademons 18y ago
It's NumOfMessages, not NumOfUsers, and Messages = Messages/User * Users. Then the question is whether Messages/User and Recipients/Message remain constant as NumOfUsers goes up. If both do, then your total cost is linear with the number of users, which is what you want. But if either of them is linear in the number of users, then the total number of messages becomes quadratic in the number of users: a linear factor from growth in userbase, and a linear factor factor from increased usage by each user. Most likely there's a logarithmic correlation (Recipients/Message goes up as more people are on the service, but not by as much as total users), which is still generally fine for scalability concerns. E-mail's actually a really great example. It worked great as long as it was used for person-to-person communication, which held both the number of messages/user and the number of recipients/message constant. Then spammers found out that the more people who had e-mail, the more they could send to at once, and sent recipients/message through the roof. In 1997/98, there were actually a number of articles about how the e-mail architecture was in serious trouble, and unless some way could be found to limit spam, it would collapse within a couple years. Of course, they dealt with it through spam filters and blacklists on the server, so now e-mail works fine. Twitter's problem is that both Messages/User and Recipients/Message average significantly higher than e-mail, and yet the resources they have available are significantly lower than the full resources of the Internet. So even if they don't have an architectural scalability problem, they could very well have an economics problem.
- hank777 18y ago
  I don't understand your correction, but my lack of understanding is really immaterial. I actually agree that twitter has a problem with economics if they cant sell anything. Whether it is worth solving the scalability problem is a good question. Certainly if they keep growing with no revenue, at some point it is definitely an economic problem. Indeed I posted a while ago about the community taking over twitter as a distributed public service (like email). I do think that there is an upper limit to the amount of messages the average user will send.

by hank777 18y ago

nostrademons 18y ago

It's NumOfMessages, not NumOfUsers, and Messages = Messages/User * Users. Then the question is whether Messages/User and Recipients/Message remain constant as NumOfUsers goes up. If both do, then your total cost is linear with the number of users, which is what you want. But if either of them is linear in the number of users, then the total number of messages becomes quadratic in the number of users: a linear factor from growth in userbase, and a linear factor factor from increased usage by each user. Most likely there's a logarithmic correlation (Recipients/Message goes up as more people are on the service, but not by as much as total users), which is still generally fine for scalability concerns. E-mail's actually a really great example. It worked great as long as it was used for person-to-person communication, which held both the number of messages/user and the number of recipients/message constant. Then spammers found out that the more people who had e-mail, the more they could send to at once, and sent recipients/message through the roof. In 1997/98, there were actually a number of articles about how the e-mail architecture was in serious trouble, and unless some way could be found to limit spam, it would collapse within a couple years. Of course, they dealt with it through spam filters and blacklists on the server, so now e-mail works fine. Twitter's problem is that both Messages/User and Recipients/Message average significantly higher than e-mail, and yet the resources they have available are significantly lower than the full resources of the Internet. So even if they don't have an architectural scalability problem, they could very well have an economics problem.

hank777 18y ago
I don't understand your correction, but my lack of understanding is really immaterial. I actually agree that twitter has a problem with economics if they cant sell anything. Whether it is worth solving the scalability problem is a good question. Certainly if they keep growing with no revenue, at some point it is definitely an economic problem. Indeed I posted a while ago about the community taking over twitter as a distributed public service (like email). I do think that there is an upper limit to the amount of messages the average user will send.