That short of a layover can make catching a connecting flight tricky. Flights of the same carrier usually board at near by gates so as long as your first flight isn't delayed you should be fine. If you connect to a different airline 30 minutes is really tight but doable.
Often the airline will hold a connecting flight if they have passengers booked from a flight that is delayed. Still if your first flight is delayed, it would be a good idea to let the flight attendant know what flight you are connecting to. Sometimes they can radio in and make sure the other plane will still be there. or have someone on the ground make alternant arraingments.