Reactive repository support gives Spring Data repositories nonblocking data-access operations through reactive publishers such as Mono and Flux. For Cassandra, the main change is extending ReactiveCrudRepository instead of CrudRepository. section 13.0 section 13.3.2
A repository interface supplies the domain type and identifier type to ReactiveCrudRepository. Its methods expose publishers: findById() returns Mono, while findAll() returns Flux. Calling subscribe() starts a Flux pipeline. section 13.1.2
Reactive Cassandra repositories
IngredientRepository can extend ReactiveCrudRepository<Ingredient, String>, while OrderRepository can use ReactiveCrudRepository<TacoOrder, UUID> and add findByUserOrderByPlacedAtDesc(User user, Pageable pageable) returning Flux<TacoOrder>. Cassandra repository tests use @DataCassandraTest and StepVerifier-style reactive verification. section 13.3.3
