I’ve used flashcards quite extensively during my studies (electrical engineering and telecom engineering) and I continue to use it for technical subjects; albeit with reduced intensity.

Spaced repetition systems are not just about “rote” memorization. When used right it is a very personalized practice tool that can help with quite high-level ideas.

I wouldn’t fx. make flashcards for an entire API — instead I would focus on the concepts and features that are important for what I am doing. You can make it about “exactly” what you want to practice and remember.

Think of it more as a collection of personal notes with build in recall practice, rather than remembering scores of “random” facts.