How to improve query performance？

[parselife]

The type of Key/Value Store is RocksDB

There are about 800 thousand features in my type , when execute a cql query, it spent about 2min, how can i improve this?
the query code snippt like :

      VectorQueryBuilder queryBuilder = VectorQueryBuilder.newBuilder();
       queryBuilder.addTypeName("xxType");
       queryBuilder.constraints(queryBuilder.constraintsFactory().cqlConstraints(cqlExpression));
       Query<SimpleFeature> query = queryBuilder.build();
       try (CloseableIterator<SimpleFeature> iterator = dataStore.query(query)) {
           while (iterator.hasNext()) {
               features.add(iterator.next());
           }
       }

Anyone can help me? Thx