-> "[" + n + "]") .flatMap(Database :: record) .retry(5); return multi .select().where(n -> n % 2 == 0) .onItem().transform(n -> "[" + n + "]") .onItem().transformToUniAndMerge(Database :: record) .onFailure() .retry() .withBackOff(Duration.ofSeconds(1)) .atMost(5); RxJava / Reactor Mutiny Functional dialect, fl at 100+ methods list Event-based dialect, group-based api