Memory lock in performcheckout seems redundant

[project-concerto]

Problem

The memory lock in CheckoutServiceImpl#performCheckout seems redundant, because lock used in CartStateFilter already prevent concurrent checkout.

Detail Description

performCheckout (Memory based lock)

Lock used in CheckoutServiceImpl#performCheckout exists in memory. It is used to prevent concurrent checkout for a same order. Before a checkout request is processed, it will acquire a lock from memory and release it after process. Once the lock can not be acquired, then the process will terminate, as show below.

protected static ConcurrentMap<Long, Object> lockMap = new ConcurrentHashMap<>();

public CheckoutResponse performCheckout(Order order) throws CheckoutException{
    Object lockObject = lockMap.putIfAbsent(order.Id, new Object());
    if(lockObject != null){
        // orderId exists in lockMap
        throw new CheckoutException("this order is already in process of being submitted");
    }
    if(hasOrderBeenCompleted(order)){
        throw new CheckoutException("order has been submitted");
    }
    try{
        // do checkout
    }
    ...
    finally{[CheckoutServiceImpl#performCheckout]()
}

CartStateFilter (Database based lock)

Lock used in CartStateFilter is based on database. Every POST requests that try to modify order (including add cart, apply offer code, and checkout), must acquire a lock on the order first.The detail logic to determine whether a request need to acquire lock for order is in CartStateFilter#requestRequiresLock.
This lock is implemented through accessing a table named BLC_ORDER_LOCK as shown below:

begin # acquire lock
select # if there is no record, then create with INSERT 
  count(*) 
from 
  BLC_ORDER_LOCK 
where 
  ORDER_ID = 88 
  and LOCK_KEY = '1a924f96-f039-4b48-ab5d-63ca7124a4ba' 

update # no rows affected means acquire lock failed 
  BLC_ORDER_LOCK 
set 
  LOCKED = 'Y', 
  LAST_UPDATED = 1604653067663 
where 
  ORDER_ID = 88 
  and (
    LOCKED = 'N' 
    or LAST_UPDATED <-1
  ) 
  and LOCK_KEY = '1a924f96-f039-4b48-ab5d-63ca7124a4ba'
commit

... # process request

begin # release lock
update BLC_ORDER_LOCK set LOCKED='N' where ORDER_ID=88 and LOCK_KEY='1a924f96-f039-4b48-ab5d-63ca7124a4ba'
commit

This lock based on database is able to prevent concurrent modification for the same order, which including checkout. Therefore, memory lock used in CheckoutServiceImpl#performCheckout is redundant

Suggestion

Maybe memory lock in CheckoutServiceImpl#performCheckout can be removed to obtain better performance.