SpellChecker implementation?

Question

Android

I set out to research a custom implementation of my spell checker on a mobile device. I ran into problems at the design level:
1. What format, type of data storage (collection of words) to use (SQLite, Realm, File)
2. The algorithm itself.
3. It would be nice to use the data structure itself to further implement your WordPredictionary.
It is clear that the answer to the first question directly depends on the second. For a mobile device, the implementation of the classic enumeration is not entirely suitable, while other implementations, their bikes based on them, consume a lot of memory and are not optimal in terms of speed.
Can anyone suggest what to do and where you can see something like that, because the task is not trivial, it was solved by enumeration methods?
PS Research:
1. AnySoftKeyboard - while I'm doing a thorough research of this source. Awesome pluses - the size of the storage of words and the speed of work. Of the minuses - a complex implementation not without NDK and a suboptimal data structure (there is no possibility to supplement the default dictionary with new words)