O.S.:Linux MYSQL server
we got a load spike last week.
how can I find the process that has created the load spike on my server last week.
You cannot triage the process that is in past-tense provided if you have below setup in-place.
By this way you can collate details when your usage goes peak. And you may check when you are awake in the day time.
If you have the slow query log active, you might be able to identify a long running query during the timeframe of your load spike. This probably the only way to figure out the issue that has already occurred.
You can configure a script like pt-stalk to try to capture future issues, however.
Here's an example to trigger data collection if you have more than 10 connections from host '10.0.0.23' [src]: