A system for periodic and real-time processing of accounts. The system operates in a bulk mode and an error mode. A bulk component concurrently processes a set of eligible accounts with a set of dependent tasks, and a removal component removes one or more accounts from the eligible accounts if an error is associated therewith. In bulk mode, each task fetches only the required set of accounts/subscriptions/payment instruments for processing. In error mode (retry/reprocess mode), if an account encounters an error for a task in the bulk mode, the account drops is removed from bulk mode and becomes ineligible for fetching in any future bulk-mode task processing. Error-mode processing tests and processes all tasks sequentially for an errored account until the account state is in par with the accounts being processed by bulk mode. Then the account is removed from error mode processing and is picked up appropriately by bulk-mode processing.