1. A method for processing a batch of input data in a fault tolerant manner, the method including: reading a batch of input data including a plurality of records from one or more data sources; and passing the batch through a dataflow graph including two or more nodes representing components connected by links representing flows of data between the components, wherein at least one but fewer than all of the components includes a checkpoint process for an action performed for each of multiple units of work associated with one or more of the records; wherein the checkpoint process includes: opening a checkpoint buffer stored in non-volatile memory at the start of processing for the batch; and for each unit of work from the batch, if a result from performing the action for the unit of work was previously saved in the checkpoint buffer, using the saved result to complete processing of the unit of work without performing the action again, or if a result from performing the action for the unit of work is not saved in the checkpoint buffer, performing the action to complete processing of the unit of work and saving the result from performing the action in the checkpoint buffer.