SmartThings won’t guarantee Execution for anything under one minute, and even then it’s not precise: it might be 55 seconds one time and 70 seconds another… So you can’t use it for super precise applications. Because it’s a cloud-based platform, just the time to get over the Internet will vary. But you can set up a rule for less than a minute using core or webcore and see if it works well enough for your needs. (you can think of Core as a scripting language for SmartThings. It will do a lot of the heavy lifting for you on complex code.)