We worked with the dev team to define a minimum loveable product for initial release as we approached exam season. 'Spaced repetition' was a hot topic in discovery, and most users requested the feature as part of Flashcards too. The algorithm was deemed complex, so we ultimately decided to proceed without it, instead opting for a faux version, that would allow users to 'bucket' cards themselves, and require them to manually filter to practice them. This was a good compromise, it meant we could ship value faster, and users loved it.