code: public boolean isValidForMemcached(final String sessionId) {
  		if ( isEncodeNodeIdInSessionId() ) {
  	        final String nodeId = _sessionIdFormat.extractMemcachedId( sessionId );
  	        if ( nodeId == null ) {
  	            LOG.debug( "The sessionId does not contain a nodeId so that the memcached node could not be identified." );
  	            return false;
  	        }
  		}
  		return true;
  	}
docs: Can be used to determine if the given sessionId can be used to interact with memcached.
  @see #canHitMemcached(String)