How to checkpoint by minibatch in Keras
You have to write a custom callback for this. Steps are :


Subclass ModelCheckpoint   (https://github.com/keras-team/keras/blob/master/keras/callbacks.py) or create new one if you do not need filename pattern etc. 
Add method that would be called at the end of each batch 



class BatchModelCheckpoint(keras.callbacks.Callback):
     def on_batch_end(self, batch, logs=None):
        self.model.save(filepath, overwrite=True)