Hi,

In a nutshell, any front-end that is configured to execute timers can execute them.

Scheduler service (running in each front-end) will pick-up the next timer to run (if any). DB is used for synchronizing this, so there's no way of two front-ends end up executing a specific timer at the same time.

In Service Center > Administration > Front-end Servers, you can configure which front-ends are allowed to execute timers (and also other asynchronous logic that is triggered by the Scheduler service as well - BPT and sending emails). You can have, for example, a dedicated front-end for executing heavy batch processing.

The configuration tool (you'll have access to it if you install the platform on-premises) also specifies a limit to the number of timers that can run at the same time. If more timers need to be executed above this limit, they will wait for an available slot.