Recovering or restarting an execution instance. In response to detecting that a particular execution instance in which a software application, such as an optical line terminal (OLT) software application or a broadband network gateway (BNG) software application, providing services for a Passive Optical Network (PON) has failed, restarting the execution instance having only downstream service flow classifiers and entries of an access control list for the particular execution instance to support default service flows and/or voice calls. After restarting the execution instance, the configuration of the instance is adjusted over time to add one or more downstream service flow classifiers or access control list entries such that the instance can provide additional services, beyond the initially supported default service flows and voice calls, to optical network units. Required time to register optical network units with the execution instance is advantageously reduced while maintaining quality of service.