I built an SRS app in Django about 16 years ago: https://github.com/thraxil/sebastian/tree/main https://github.com/thraxil/sebastian/tree/main and have been usi

I built an SRS app in Django about 16 years ago: https://github.com/thraxil/sebastian/tree/main https://github.com/thraxil/sebastian/tree/main and have been using it ever since. The core part of the business logic is here: https://github.com/thraxil/sebastian/blob/main/sebastian/leitner/service.py#L10-L110 https://github.com/thraxil/sebastian/blob/main/sebastian/lei... It's not as terse as the SQL, but I think it's pretty easy to understand and it's proven itself over 16 years of regular use (currently around 12k cards learned). For each card, I track the rung, which more or less determines the interval, set a due date on the card after it's tested mostly just using the intervals from Sebastian Leitner's original research. Then, I can always just select the card with the closest due date < today.