Stats
* 60 messages per second
...
* 26 front end proxy serves. Double that in backend app servers.
We have one MSSQL box at work here that is regularly doing 2,500 queries/sec and that's an OLTP workload so easily more than 60 writes/sec.
serves makes me think that someone didn't proof-read the article...
The proxy servers are there to terminate the large number of persistent connections. Of course it's possible to do it using less servers, but given the Hipchat guys are smart (disclosure - I'm an Atlassian and know the internals) I would give them the benefit of the doubt rather than engaging in armchair architecture.
Practically speaking the number of frontend servers is related to the number of active listening clients and not messages.
Only 60 messages per second does seem very small from a business perspective however.
When all of these factors are considered, 52 servers isn't a huge number.
https://s3.amazonaws.com/uploads.hipchat.com/10804/368466/10...
That traffic is going to be highly bursty, though.
I imagine an outsider wouldn't equate "childcare software" with "database intensive" but the online reporting childcare services have to do is quite involved [1].
Their online reporting to the government is a separate concern to day-to-day tasks in their childcare service. So childcare software has to do more than just interface with the online reporting interface.
[1] http://docs.education.gov.au/system/files/doc/other/service_... (The attendance information of children is the most complicated part, see page 160 for what an attendance record looks like.)