In addition to choosing a submission limit, projects allow you to specify a cooldown period that takes effect after the student's first submission. We have defaulted this feature to five minutes on new projects but you can increase or decrease the wait time or turn it off altogether. Students still get immediate feedback on their submissions on the performance of their code against your test cases.
Projects with cooldown period will inform the students at the top on the submissions page and will warn them before submitting that there is a cooldown period and how long it is.
After submitting, students have real-time feedback on how much longer they have to wait until the next time they can submit. Feedback from multiple universities suggested that instructors could benefit from this to encourage students to test their code before submitting. Students can still edit and run their code through the IDE, if enabled, as usual during the cooldown period.