The IT Constants

Thinking about estimating and realism, I wondered if anyone had listed out what I think of as the IT Constants…

There are some generic ones — anyone who can’t recognise 1440 and 99.93 needs to go and learn more about their support operation. If you recognise 86400 then you’re doing moderately well; if you recognise 604800 you’re doing very well and if 604800000 is familiar you should get out more or stop programming calendar code.

Then there are your business’s order-of-magnitude “constants” – transactions per peak 15m, online sales per day, percentage online fulfilment, and so on. Those are the tricky ones — they’re not constants, because your business people are busy trying to change them (while you’re trying to do capacity management), but they crop up in lots of your rules of thumb. How often should you revisit them? In an ideal world, wouldn’t you like them on a dashboard on your phone?