>> Yes, SELECT. Can you try yourself ? Construct SELECT statement with WHERE
>> clause that will return e.g. 150 rows,
>> and execute it on your 50 000 000 records table, once ORDERed by index,
>> once withou index, and compare the times.

...

> "first rows" could be faster when using the index though, can't it Ivan?

Yes, but not as fast as one would expect (i.e. the 100 ms limit will most probably be exceeded)

Ivan