It assigns priorities to processes based on their slack time.
This scheduling algorithm first selects those processes that have the smallest "slack time".
One of the simplest acceptance tests for a sporadic job is calculating the amount of slack time between the release time and deadline of the job.
LST scheduling is most useful in systems comprising mainly aperiodic tasks, because no prior assumptions are made on the events' rate of occurrence.
The main weakness of LST is that it does not look ahead, and works only on the current system state.
However, like the earliest deadline first, and unlike rate monotonic scheduling, this algorithm can be used for processor utilization up to 100%.