Design Pattern LLD

Sample interview Question in LLD.

Part 1.

Implement and verify the implementation of the following 3 classes.

The Customer class should have - id and name. The Transaction class should be immutable and should have two mandatory fields and one optional ones. Mandatory Field - details, amount, timestamps. Optional Field - channel.

Te optional field can be increased later part. The mandatory field is not present then it should generate the error. The TransactionRegistry class is a singleton. Its purpose is to store the relationship between Customer and Transaction.

void registerTransactionForCustomer(Customer c, Transaction trx){}

List<Transaction> getTransactions(Customer c){}

Additional Requirements.

Only the unique transactions can be stored per customer - unique pairs of details and timestamp.

getTransactions method should returns the tranactions ordered from the oldest one.

@Getter
@Setter
@AllArgsConstructor
public class Customer{
    private String id;
    private String name;
}