A reliable virtualized network function, rVNF, system for a cloud computing system, comprising: a virtualized network function, VNF, application instance that comprises a plurality of physical VNF instances ; a load balancer that provides an interface between a client and the VNF application instance ; a load balancer interface between the load balancer and the VNF application instance , the load balancer interface adapted to deliver packets related to a particular user context to a same physical VNF instance of the plurality of physical VNF instances ; a communication interface between the load balancer and the VNF application instance , the communication interface adapted for communication between the client and the VNF application instance ; and an application storage that stores session data associated with the VNF application instance ; characterized in that : the application storage comprises a transactional key-value store , wherein a list of local copies of accessed key and value pairs is created at a start of a transaction; and modifications to the accessed key and value pairs are made in the list of local copies until the transaction is committed; and in that the load balancer interface comprises a non-transactional key-value store in a load balancer storage , wherein in response to receiving an incoming packet the load balancer interface : parses the incoming packet and extracts metadata from the incoming packet ; searches for the metadata in the load balancer storage and identifies a physical VNF instance that is associated with the metadata; and forwards the incoming packet to the identified physical VNF instance . a virtualized network function, VNF, application instance that comprises a plurality of physical VNF instances ; a load balancer that provides an interface between a client and the VNF application instance ; a load balancer interface between the load balancer and the VNF application instance , the load balancer interface adapted to deliver packets related to a particular user context to a same physical VNF instance of the plurality of physical VNF instances ; a communication interface between the load balancer and the VNF application instance , the communication interface adapted for communication between the client and the VNF application instance ; and an application storage that stores session data associated with the VNF application instance ; characterized in that : the application storage comprises a transactional key-value store , wherein a list of local copies of accessed key and value pairs is created at a start of a transaction; and modifications to the accessed key and value pairs are made in the list of local copies until the transaction is committed; and in that the load balancer interface comprises a non-transactional key-value store in a load balancer storage , wherein in response to receiving an incoming packet the load balancer interface : parses the incoming packet and extracts metadata from the incoming packet ; searches for the metadata in the load balancer storage and identifies a physical VNF instance that is associated with the metadata; and forwards the incoming packet to the identified physical VNF instance . the application storage comprises a transactional key-value store , wherein a list of local copies of accessed key and value pairs is created at a start of a transaction; and modifications to the accessed key and value pairs are made in the list of local copies until the transaction is committed; and in that the load balancer interface comprises a non-transactional key-value store in a load balancer storage , wherein in response to receiving an incoming packet the load balancer interface : parses the incoming packet and extracts metadata from the incoming packet ; searches for the metadata in the load balancer storage and identifies a physical VNF instance that is associated with the metadata; and forwards the incoming packet to the identified physical VNF instance . <EOS>