R' Keruspadai's teaching - 4 interpretations:
1) Tosafot - 'Life' and 'death' in World to Come (WtC), not in this world. Each RH, G-d decides whether the individual merits to be given 'life' in the World to Come or not. The person who merits at RH to enter the WtC i.e. life, may be sentenced to a year of suffering so as to cleanse those few sins from their balance sheet, thereby allowing him to enter the WtC without any further cleansing in Geihennom.
A wicked person may receive a year of 'bliss' as reward for his few good deeds, thereby depriving him of WtC. VILNA GAON agrees with this view. According to this approach, NO one is sealed until YK.
2) RambaN (Nachmonides) - Life & death (in THIS world). Tzaddik - Someone who emerges with favourable judgement. Rasha- Emerges with unfavourable judgement. Does NOT refer to them i.t.o. number of good deeds or sins they might have. acquired up until that day. One bad deed could result in one being classified a Rasha even though the person lives a committed life of Torah & Mitzvot. Similarly, a person completely devoid of good deeds could do ONE good deed and be counted according to Hashem as a 'tzaddik'.
3) RAAVAD- Each person is born with an allotted life span. Every Rosh Hashanah, the allotment comes up for review. (ADAM, who was destined to live 1000 years, 'gave' 70 years to KING DAVID).
4) SEFER HACHINNUCH/PNEI YEHOSHUA- Completely righteous are those that have ZERO sins. Completely wicked are those that have ZERO good deeds. They are sentenced to life and death. EVERYONE else, even 1 sin or 1 good deed, are considered Beinonim (in betweeners).