After reading data, you should commit the offset of the last message read from each partition so that your application can resume reading new messages from the correct partition in the event that there is a disruption to the subscription, such as an application crash. An offset can also be useful if you delete a subscription then recreate a subscription for the same layer, because the new subscription can start reading data from the offset. To read messages already committed, use the /seek endpoint, then use /partitions. The base path to use is the value of 'nodeBaseURL' returned from /subscribe POST request.