How do I handle a million hits a minute?
scumola: It all depends on how "lean and mean" your app and the data is.  If you do everything in javascript up-front and use AJAX to move data back and forth, then you reduce the pure bandwidth except for the initial javascript load (which you could cache on Akamai or something).Some math:  Sustained (theoretical maximums) with a 1Gbps link gives you 1M hits per minute at 8053 bytes per hit max.  However, you're going to get less than this in reality.  Figure 80% of this (6442 bytes) is what you can expect on average.  A Gigabit pipe is also big bucks.You'll need > 1 web server to handle the CPU load to handle 1M hits per minute, so you'll need a load-balancer that can handle Gigabit (Major $$$ already - we're talking in the $50k-$100k just for a single load-balancer that can handle this kind of traffic and most enterprise load-balancers max-out at one million 'sessions' (open connections)), so you may need to address multiple load-balancers running in an active/active configuration and > 1Gbps pipe if you are moving > 8k per 'hit'.  Keep in mind that there is connection time/bandwidth overhead and http packet overhead as well.  If you could get away from the browser/http model and move to more of a client/server application, you could optimize better and make better use of your bandwidth.  Just a thought.  Switching to a UDP protocol could save you bandwidth and make things a little faster network-wise also.To be speedy, your app will have to live without a traditional DB.  Put the data in memory (easy to do with memcache across several machines) and make sure that your app is quick and avoid using anything else that would be sub-optimal.  Use a lightweight web server, or just get your app to take the http requests itself.  C is a good choice for squeezing as much as you can out of your CPU.  Write key/value pairs to memcache as your DB, and you should end up with a 10ms turnaround with your app if there is not too much calculation to be done (no sorts, no big/nested loops, ...).  Perhaps an apache module for your app would be in order here?  Get a few machines maxxed-out with this configuration (need 6+ just as an initial guess, depending on the load-balancer and network latency to serve all of those requests in a second), and it's do-able.  Buy reliable machines (DELL or the like) and reliable network equipment since you'll be pushing the hardware to their limit and they'll be running hot.Instead of writing to a conventional database, you can write to a log file or syslog to another machine (1M writes a minutes shouldn't be that bad) and reconstruct the data to a database when the heavy usage slows down (process the log files offline or something on a different machine).This is not a small task and will require some tight code and big $$$ up-front, but it's doable.  Your Co-location bill will be large.