Adding to what bladecatcher said, even if you want to work internally with a binary format, the fact that you receive large csv datadumps from the outside means

Adding to what bladecatcher said, even if you want to work internally with a binary format, the fact that you receive large csv datadumps from the outside means you'll have to transform them into your internal format of choice. The first part of that transformation would greatly benefit from a fast csv parser such as ParaText. Another datapoint: data changes (price updates, number ranges) between European telecom operators are all csv files over ftp. You can recognize the security aware by their use of sftp!