Mixing in key: basic questions

[Ever]

Returned to DJ'ing after a decade off, and now I see that mixing in key is really popular.

I've read up on the scales, but I have a question about the execution:

Doesn't pitch adjusting for beat matching throw everything off?

For example, I've brought all my music into Rekordbox, I know the keys, I'm good to go. But I still have to beat match, so everything will be thrown off if I plan a set based on key as the BMP's don't match.

Is key lock the only answer to this?

[soundinmotiondj]

In general, it takes a 6% change to change one full key. So, in general, a +/- 3% pitch change can be safely made on both songs in a mix without altering the key to the point that they might clash. However, keep in mind that moving one full key (or from major to minor) can still be done while harmonically mixing. In the cases that you want to progress through key changes...then +/- 6% changes can be made, if you can coordinate the key progression of the songs.