Android development requires modern solutions, a mobile applications store big amount of data. SQLite project, a default Android database engine was launched in 2000 and has some alternatives like pretty popular Realm and quite new ObjectBox. Both products comprise NoSQL database and have a few things in common: DB built for objects, ACID properties, Multiversion Concurrency Control (MVCC) architecture, core written in C++, reactive data observation and a multiplatform.
Both libraries respect ACID, are MVCC and work on objects. However, the approach to the transaction is at variance. ObjectBox is easy to use and offers limited options along with write transactions that are implicit by default. Realm, in turn, exhibits more options from which to choose a better fit for a particular dev's case. Both libraries seem like a good alternative for SQLite, but the decision which one to use should be in sync with your individual needs.