Optimizing data model to be stored in data grid with less cache size

[Ferry Syafei Sapei]

If I have for instance the following data model to be persisted in the data 
grid:

class Person {
        String accountNumber;   // accountNumber is also the cache key
        String name;
        String birthday;
        String addressPostcode;
}

Should I replace the String data type to another data type in order to reduce 
the cache size?

Does Ignite perform some optimization when it persists the data in the cache?

I tried the following optimizations, but they did not really affect the cache 
size:
- replace accountNumber’s data type to long
- replace name's data type to byte[]
- replace birthday’s data type to long