There are two critical aspects to scalability:
- In single user-mode: will the response time next year be the same as it is this year (see Philosophy – 3)
- In multi-user mode: will the response time be the same when the number of users doubles, trebles, quadruples …
If you want that as a snappy catch-phrase Cary Millsap produced a good one at Collaborate 2009: “Fast Now, Fast Later”.
