Want to clear particular cache by using cache key in business rule

[RajeshkumarV]

Basically, I am trying to override function: getMySubscriptions from script include: ServiceSubscriptionUtilsSNC, because I want to add few more conditions on 

_addGroup function.

var SUBSCRIPTIONS_CACHE = 'SUBSCRIPTIONS_CACHE';


        // check the SUBSCRIPTIONS_CACHE if the there is an offering sys_ids array already associated to the user
        var userCachedSubscriptionsArr = sn_scoped_cache.ScopedCacheManager.get(SUBSCRIPTIONS_CACHE, userId);
  if (userCachedSubscriptionsArr)
            return JSON.parse(userCachedSubscriptionsArr);

I want to clear this SUBSCRIPTIONS_CACHE cache for particular user from business rule.

Tried the following, but didnt help.

Option_1:

var sm = GlideSecurityManager.get();

            sm.setUser(gs.getUser());

Option_2:

sn_scoped_cache.ScopedCacheManager.flushScopedCache("SUBSCRIPTIONS_CACHE");

Option_3:

var user = gs.getUserID();

sn_scoped_cache.ScopedCacheManager.flushScopedCache("SUBSCRIPTIONS_CACHE", user);

the only thing working as expected is, full flush: 

gs.cacheFlush();

But full flesh is not recommended. Please suggest any other approach. Thanks in advance.