A TFRecords file represents a sequence of (binary) strings. The format is not random access, so it is suitable for streaming large amounts of data but not suitable if fast sharding or other non-sequential access is desired.
TFRecords Format Details
A TFRecords file contains a sequence of strings with CRC32C (32-bit CRC using the Castagnoli polynomial) hashes. Each record has the format
uint64 length uint32 masked_crc32_of_length byte data[length] uint32 masked_crc32_of_data
and the records are concatenated together to produce the file. CRCs are described here, and the mask of a CRC is
masked_crc = ((crc >> 15) | (crc << 17)) + 0xa282ead8ul