• Append only file for changes that will be made to the database.
  • Before applying changes, write to WAL first
  • Implement record structure
	length: uint32      // length of data section
	checksum: uint32    // CRC32 checksum of data
	data: byte[length]  // serialized ddb.internal.LogRecord proto
  • Periodically perform checkpoints (Database Recovery), which involve writing all the changes specified in the WAL to the database and clearing the log.