[blattimwind]

I might add, those processes have little to do with SQL. When you have a lot of data, and a lot of queries, then you're going to have to monitor and optimize your databases.

I might also add that a basic understanding of data modelling and what an index can and can't do is sufficient to avoid many, many performance pitfalls (this again has mostly nothing to do with SQL per se). Any undergrad course on databases teaches these basics.

[barrkel]

The variance provided by an enormous pile of state and an algorithm which uses that state means it's a bit more unpredictable than most other systems, where you're used to seeing lines, curves and almost always monotonic series.