Cassandra-quarkus-client hangs at quarkusCqlSession.prepare

I spotted problem with Quarkus CqlSession. When i calling method "prepare" its hang and timeout. Code snippet:

    @Inject
public NewsEngineRepository(QuarkusCqlSession quarkusCqlSession, NewsEngineConfig newsEngineConfig, Logger log) {
    queryLimit = newsEngineConfig.dbQueryLimit();
    this.quarkusCqlSession = quarkusCqlSession;
    this.log = log;
    SimpleStatement ss = SimpleStatement.newInstance("select " + ITEMID + ", " + PUBDATE + " from news_engine_items where defverid = ? AND group = ? Limit  " + queryLimit);

    preparedStatement= quarkusCqlSession.prepare(ss); // <---- hangs here

    this.log.info("Prepared statement created successfully: " + ss.getQuery());
}

I found a two solutions:

1. Increasing property quarkus.vertx.eventLoopsPoolSize from 2 to 4
2. Setting properyty quarkus.cassandra.use-quarkus-event-loop to false

Can anyone explain why solution 1 works?