We use REST API Transaction for 2-3 steps transactions.

They took usually up to 5 seconds.

The highest frequency for  this type of monitors is 10 minutes.

Having very tight SLA'a it is to less. 

We need to have 1 and  5 minutes frequency.

In addition this type of monitoring should have a simple shell access to be able to run basic & simple scripts (otherwise it is difficult to use this feature comparing to  jMeeter and Zabbibx).

Regards,

Marek Kowalczyk