What performance fluctuation to expect from a Shared CPU on DO?

Hey,

We are running a microservice on a shared CPU droplet. This microservice performs occasional, long running, CPU intensive background tasks. The time it takes for a task to finish depends on input, and can take from 10 seconds to an hour (or even more), depending on its complexity.

Because the input data is technically user-provided, I’d like to apply a time duration limit. Say, the task is allowed to run for 30 minutes, and if it’s still not done by then, it’s rejected and marked as non-processable.

However, on a shared CPU, it’s well understood that the available processing power is effectively unknown. Thus, in this case, the very same task can take a different duration to finish.

We want to take this into consideration when deciding on a limit, but for that, a rough estimation of CPU power fluctuation is needed.

Does anyone have any experience as to what to expect here? Say, is there a rough threshold of CPU power that’s always available in practice? For example, can we expect CPU power to be at least 20% of its peak capabilities at all times in practice?

Thanks in advance.

PS: I know simply switching to a dedicated CPU would make this a non-issue, but currently it’s way above our requirements.