AsyncRx.java

    // and then the age of enlightenment
    private Map<String,String> getMappingTable() {
        // You only want to prepare the query once. Best to do it when you initialize the session.
        PreparedStatement findMappings = session.prepare(
                "SELECT project_id, project_name " +
                "FROM openshift_metrics.metrics_mappings " +
                "WHERE token(project_id) > ? AND token(project_id) <= ?");

        RxSession rxSession = new RxSessionImpl(session);

        Map<String,String> mappings = new HashMap<>();
        if (hasMappingTable()) {
            Observable.from(getTokenRanges())
                    .flatMap(tokenRange -> {
                        BoundStatement boundStatement = findMappings.bind().setToken(0, tokenRange.getStart())
                                .setToken(1, tokenRange.getEnd());
                        return rxSession.execute(boundStatement);
                    })
                    .flatMap(Observable::from)
                    .collect(HashMap::new, ((map, row) -> map.put(row.getString(0), row.getString(1))) )
                    .toBlocking()
                    .firstOrDefault(new HashMap<>());
        }

        return Collections.emptyMap();
    }