Anki
Anki is a free software (Windows/Mac/Linux/iPhone/Android) designed to help remembering information. Anki relies on the concept of spaced repetition which is a proven technique to increase the rate of memorization. Here's a 2-minute video that delves into spaced repetition:
Michael A. Nielsen, "Augmenting Long-term Memory"
The single biggest change that Anki brings about is that it means memory is no longer a haphazard event, to be left to chance. Rather, it guarantees I will remember something, with minimal effort. That is, Anki makes memory a choice.
I used Anki myself with Algo Deck and Design Deck and it paid off. This method played a key role in helping me land a role as L5 SWE at Google (senior software engineer).
Here is a flashcard example:

The Anki versions (a clone of the flashcards from this repo) are available via one-time GitHub sponsorships:
Trusted by over 100 developers.