Theoretical situation about MySQL
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I searched Google for a question I ask myself since this morning but couldn't find any information or article about it.

I was wondering, in the following situation, to improve performance (a little % still) :

**Context:** I have two column : `ID`, `AddedAt` (`AddedAt` is the Unix Timestamp of when the row is created).

Theoretically, if you insert a new row, `ID` will be +1 and `AddedAt` will be the current time.

Now, let's say it is impossible in the current situation to have two simultaneous insert, would it be better to use `AddedAt` as  a `PK` and remove the `ID` column ? `AddedAt` will be only one and unique column that does `PK` and `UNIX Timestamp`. So in the final, I will have one column instead of two.

The only bad side I see is maybe the size of the key that will be created on `AddedAt` since unix timestamp now's day is 10 digits.

Would it be better, in this situation ? What's your opinion ?